Sai in One Piece

Sai, along with Boo and Chinjao, arrived from the Kano Country to compete in the Corrida Colosseum for the Mera Mera no Mi Devil Fruit. They also had a hidden agenda to investigate a weapons trade involving the Donquixote Family.

During the competition, Sai was placed in Block C. When Lucy (disguised as Monkey D. Luffy) defeated Spartan before the official start of the match, a colosseum staff member threatened to disqualify him for starting a fight. Sai and Boo from the Chinjao Family intervened, defending Lucy and insisting that the blame should be placed on the "big guy" (Spartan) who initiated the brawl.

Despite the initial tension, they helped Lucy and Sai humorously demanded that Lucy take back his thanks. Later, when Chinjao attempted to kill Lucy due to his vendetta against Monkey D. Garp, Sai and Boo restrained Chinjao to prevent him from losing control of his anger. They reminded him of their true mission and goal, suggesting that they could deal with Lucy during the competition.

Sai and his family then entered the ring, ready to participate in Block C's battle royale. During the battle, Sai observed as Lucy (Luffy) defeated various competitors while riding on the back of Ucy, a giant bull.

Shortly after entering the Colosseum, Sai demonstrated his martial arts skills. He used his polearm to dodge an opponent's attack by pole vaulting and then disarmed and defeated the fighter with a powerful kick, utilizing the Hasshoken technique.

When Boo was being brutally attacked by the Funk Brothers, Sai expressed alarm and later avenged his brother by knocking out the Funk Brothers with a single kick. After this victory, he engaged in a battle with Ideo, and the two fighters appeared evenly matched, exchanging blows.

Before either Sai or Ideo could finish each other off, they were interrupted by Lucy (Luffy) and Chinjao's feud. Lucy knocked Sai out of the ring with a single kick while charging at Chinjao. Sai ended up floating on the water outside of the ring with Boo, watching Chinjao's intense battle with Lucy.

They called out to Chinjao in horror as he was defeated and fell into the water. After the match concluded, Sai and Boo brought the defeated Chinjao to Luffy so he could thank him for restoring his old head using Haki. They showed gratitude towards Luffy for this act.

Later, in the underground medical treatment facility, Sai was seen in the waiting room, impatiently waiting for Chinjao to finish his treatment. He became agitated and yelled at a doctor for not allowing him to see his grandfather. However, he was informed that Chinjao had already left through another exit, and he apologized for his earlier outburst.

When it was Sai's turn for treatment, he laid on the examination table, which turned out to be a trapdoor that dropped him into an underground dungeon filled with broken toys. Sai found himself trapped with other disqualified participants and demanded to know what was going on and how they could escape.

Sai found himself trapped in the underground dungeon along with other defeated contestants, including his brother Boo, after falling through the trapdoor. He could only watch as more contestants were dropped into the dungeon.

During their time in the dungeon, it was revealed that Ricky, one of the contestants, was actually the former king of Dressrosa, Riku Doldo III. Sai took this opportunity to express his anger and blame King Riku for allowing Doflamingo to rise to power, which ultimately led to wars in various countries, including the Kano Country. Sai's resentment toward King Riku was fueled by the suffering caused by Doflamingo's actions in various nations.

However, Sai's anger was cut short when he was abducted by Trebol, one of Doflamingo's top executives, and transformed into a toy using the powers of the Hobby-Hobby Fruit (Hobi Hobi no Mi). As a toy, Sai became obedient to Trebol's commands and lost his free will.

While transformed into a toy, Sai was seen working in the underground trade port, moving crates and following orders without question. It was a stark contrast to his previous strong-willed and outspoken personality.

Sai's transformation back into a human occurred when Sugar, the user of the Hobby-Hobby Fruit, lost consciousness, reverting all the transformed toys back to their original forms.

Once freed from his toy form, Sai rejoined the Chinjao Family and other colosseum fighters who had also been transformed into toys. They decided to team up with Luffy's group, along with other powerful allies, to take on Doflamingo and his forces.

They made their way towards the royal palace, where Pica, one of Doflamingo's top executives, confronted them in his giant stone form. Sai and the allied fighters engaged in battles against Doflamingo's troops and Pica's stone giant form.

They fought valiantly and worked together to overcome various challenges and obstacles as they advanced towards their goal of defeating Doflamingo and liberating Dressrosa. As the colosseum fighters continued their ascent to the King's Plateau, they faced off against the Donquixote Pirates' troops who tried to stop them.

With Zoro taking on Pica and Sabo dealing with the Marines, the colosseum fighters played a crucial role in advancing toward their goal. Upon reaching the first level of the plateau, the colosseum fighters moved ahead of Luffy, setting the stage for their confrontation with the Donquixote Pirates.

As they progressed to the second level, they encountered four of the Donquixote Pirate officers, who attempted to impede their progress. The colosseum fighters collaborated to create an opening for Luffy and Cavendish, showcasing their teamwork and determination.

During the chaos, Sai found himself facing off against Baby 5, one of the Donquixote Pirate officers. Their battle ensued, with Sai using his staff to block Baby 5's bladed kick. However, their interactions took an unexpected turn when Baby 5 misunderstood Sai's words and thought he was hitting on her.

Sai attempted to clarify that he had no intention of marrying Baby 5, as he already had a fiancée from the Niho Navy. Despite his rejection, Baby 5 continued to believe that Sai needed her attention. In a surprising twist, Baby 5 began to genuinely consider taking her own life, prompting Sai to rush to stop her from self-harm.

Chinjao, witnessing the situation, grew furious that Sai was helping an enemy. He attempted to attack both Sai and Baby 5 with his pointed head. In response, Sai delivered a powerful kick that bent Chinjao's head and slapped Baby 5, putting an end to the confusion.

Chinjao, recognizing Sai's strength, granted him the title of Don. However, their moment of acknowledgment was cut short when Lao G launched a surprise attack on Chinjao. Sai vowed to marry Baby 5 after defeating Lao G, and as Lao G charged at him, Sai managed to defeat his opponent with a decisive kick to the head.

After the intense battle with Lao G and surviving Pica's crushing attack, Sai attended to Chinjao's injuries. Baby 5's comment about preparing for both a wedding and a funeral annoyed both Sai and Chinjao, as the latter was still alive despite the close call.

Sai, along with Chinjao and Baby 5, watched in amazement as Pica transformed into an enormous stone giant and headed toward the Old King's Plateau. Witnessing Pica's eventual defeat at the hands of Zoro left Sai awestruck by the swordsman's incredible strength.

As Dressrosa faced the impending danger of the Birdcage shrinking and causing chaos throughout the island, Sai noted the tremors and smoke produced by the collapsing Birdcage. He urged his fellow gladiators, including Chinjao, Orlumbus, and Elizabello II, to wake up their fallen comrades and ensure their safety.

With Mansherry temporarily healing the injured fighters, Sai and the other gladiators teamed up to defeat the remaining Donquixote Pirates on the New King's Plateau. Their efforts were instrumental in helping the citizens escape from the encroaching Birdcage.

When the Birdcage approached the central streets, the gladiators collaborated to push it back, using Bartolomeo's barrier to slow its advance. Once Luffy defeated Doflamingo, the Birdcage collapsed, ending the crisis.

In the aftermath of the battle and Dressrosa's liberation, Sai and the other gladiators rested at the palace, with Baby 5 seeking comfort by his side.

Three days after Doflamingo's defeat, Sai and the other gladiators prepared to assist the Straw Hats in their escape from Dressrosa, as the Marines were mobilized to pursue them.

As the Straw Hats made their way to the eastern port, Sai and his fellow gladiators stood in the way of the pursuing Marines. They gathered at the eastern port, preparing to confront Admiral Issho (Fujitora). When Issho began using his gravity abilities to launch rubble from Dressrosa, the fighters quickly boarded the escape ship. Sai was astonished when he witnessed Luffy using a Haki-imbued Gear 3 attack to clash with Issho.

During the intense confrontation, Issho unleashed his gravity powers, causing Luffy to be blown away and caught by Hajrudin. The fighters and Straw Hats made their escape across a bridge that led to a massive ship in the distance. As they reached the ship, Dressrosa citizens, pretending to chase Luffy, obstructed Issho's attack. Eventually, they boarded Orlumbus' flagship, the Yonta Maria. Onboard the ship, Sai's Happo Navy was one of the seven groups that pledged their allegiance to the Straw Hats.

When Luffy declined to perform a sakazuki ceremony for the alliance, there was initial shock among the allies. However, Luffy clarified that they could do as they pleased, and they decided to forge the alliance regardless, officially forming the Straw Hat fleet. Sai, along with Bartolomeo, Leo, Cavendish, Ideo, Orlumbus, and Hajrudin, participated in the ceremony, drinking sake cups to seal the agreement. Afterward, they celebrated their victory over Doflamingo with a feast.

Following the festivities, Sai and the other leaders received Luffy's vivre card and bid farewell to the Straw Hats. Sai and the Happo Navy then embarked on their journey back to their home country.

The Stories of the Self-Proclaimed Straw Hat Grand Fleet

Upon returning to Kano Country, Sai had a conversation with Uholisia, which led to him breaking off their engagement. Uholisia, infuriated by this decision, proceeded to give Sai a beating. Covered in bandages from the altercation, Sai and Baby 5 went on to have their wedding, marking a significant event in their lives.

Levely Arc

Sai's involvement in world events continued as he attended the Levely in Mary Geoise. During this gathering of royalty and leaders from various nations, Sai had the opportunity to reunite with Rebecca and Leo. He confided in Leo, sharing his plan to sever ties with his home country after the Levely.

However, tensions escalated when Charlos, a World Noble, attempted to forcibly take Shirahoshi. Sai found himself in a challenging situation as he had to restrain Rebecca to prevent her from provoking the World Noble. When Leo rushed to rescue Shirahoshi, Sai came to his aid, but their efforts were thwarted by the intervention of Rob Lucci.

Mjosgard, a Celestial Dragon who sympathized with the Neptune Family, stepped in to protect Shirahoshi during this crisis.

Wano Country Arc

When Charlos made another attempt to enslave Shirahoshi, Sai and Leo, recognizing that they were pirates without countries to worry about like the Neptune family, sought Mjosgard's permission to confront Charlos. Mjosgard agreed to take responsibility for their actions.

In response, Sai and Leo unleashed their attacks on Charlos, resulting in the World Noble's head being flattened and causing panic among the nearby witnesses who feared that Charlos had been killed. Bartholomew Kuma, a Warlord of the Sea, attempted to retaliate against the pirate duo, but Morley intervened, saving them. Sai and Leo proudly declared themselves as commanders of the Straw Hat Grand Fleet, solidifying their allegiance to Luffy's cause.

The incident was reported as an attempted murder plot, causing a stir during the Levely proceedings.

Sai is a man who strongly believes in honesty and fairness, and this sense of justice is a central part of his character. He values integrity and fairness in all aspects of life. This is evident when he stood up for Luffy when he believed he was about to be unfairly disqualified in a tournament, highlighting his commitment to doing what's right.

Emotionally, Sai is quite expressive and tends to overreact when rejecting something or apologizing. He can be stubborn about refusing offers, repeatedly insisting that there's no need for them before becoming confrontational with the offering party. This emotional intensity also extends to his sense of responsibility.

He takes his role as the commander of the Happo Army seriously and is dedicated to his comrades in arms. He will not hesitate to seek vengeance on behalf of his fellow soldiers if they are defeated.

Despite his dedication to training in the Hasshoken martial art, Sai has a compassionate side. He possesses a strong sense of honor, even when dealing with his enemies. He opposes underhanded tactics and seeks to win battles with fairness and integrity. This compassion is evident when he tried to prevent Baby 5 from committing suicide, as he didn't want to win in such a way.

He was also quick to defend Baby 5 when she was insulted by Lao G and was willing to take a brutal attack from Pica to protect her. Furthermore, Sai's compassion extends beyond his immediate allies. He has a strong sense of justice and is willing to defy even the World Nobles to help people in need, as seen when he backed up Leo's attempt to save Shirahoshi from Charlos, despite the potential consequences of defying the World Nobles.

Sai's unique laugh, "Kakakaka," adds to his distinctive personality traits, making him a memorable character in the One Piece world.

Sai is a robust man and has shaggy brown hair that frames his face, along with sideburns that add to his rugged look. One of his notable physical features is his smooth and tubular torso, which lacks the typical definition of abs or a belly button, giving him a unique and somewhat surreal appearance.

His attire includes a dark green cape with a white frill collar, which adds a touch of flair to his outfit. Sai's pants are puffy and feature bold blue and yellow thick stripes, though they are green in the manga. Completing his look are his black shoes.

A significant tattoo adorns Sai's left side, just below his ribs, displaying the number "13." This tattoo signifies his position as the 13th leader of the Happo Navy, emphasizing his leadership role within the organization.

In his transformed state as a toy, Sai takes on the appearance of a monkey equipped with cymbals. Despite the transformation, some elements of his human appearance are still recognizable.

He retains his rounded teeth, well-defined lower jaw, and wears distinctive accessories such as a bow tie, sunglasses, a striped hat, and a pair of pants that resemble those he wore as a human. Unlike many other transformed toys, Sai's toy appearance vaguely resembles his human self, making him somewhat recognizable even in this altered form.

Sai, the 13th Commander of the Happo Navy, possesses both authority over his subordinates and remarkable combat abilities. He demonstrated his formidable strength by defeating the Funk Brothers with a single kick, despite their reputation for taking down pirates with bounties exceeding 100 million.

Furthermore, Sai managed to defeat Lao G, a powerful executive from the Donquixote Pirates, using a Haki-imbued kick that shattered the ground. His grandfather, Chinjao, whose bounty once exceeded 500 million, acknowledged Sai's superior strength. Even Roronoa Zoro, a member of the Straw Hat Pirates, was impressed by Sai's destructive power and took note of his name for future reference.

Sai's training in Hasshoken, a unique martial art that infuses physical strikes with vibrations, granted him tremendous physical prowess. He specialized in employing vibration-enhanced kicks, which proved highly effective. Alongside Boo, he managed to restrain his enraged grandfather Chinjao. This feat demonstrates his proficiency in Hasshoken and his ability to apply it strategically.

Sai's combat prowess extends to the challenges of the New World, where he serves as the 13th Commander of the Happo Navy, succeeding the legendary Chinjao. In the Block C battle royale of the Corrida Colosseum, he showcased remarkable agility, easily evading the combined assault of the Funk Brothers and defeating them with a single blow.

He also engaged in a spirited battle with Ideo, a powerful boxer capable of launching giants out of the ring with a single punch. While Luffy knocked Sai out of the arena with a surprise Gear 2nd kick, he quickly recovered, indicating his resilience.

Sai's true strength became evident when he effortlessly bent Chinjao's Haki-coated head, a feat previously accomplished only by Garp and Luffy. During his confrontation with Lao G, Sai defeated him handily and generated enough force to split an entire hill in two with the aftershock of his attack. His grandfather noted that Sai possessed the power to break through ice sheets, much like he did 30 years prior.

Sai has demonstrated proficiency in Busoshoku Haki, as evident when he coated his leg with Haki during battles with Chinjao and Lao G. He can also extend Haki to cover large portions of his body, providing protection against formidable opponents like Pica. Additionally, he possesses Kenbunshoku Haki, enhancing his overall combat awareness.

In terms of weaponry, Sai has shown proficiency with a sword and a bladed polearm. He exhibits acrobatic skills with the polearm, using it as a platform for launching himself at foes and delivering devastating attacks.

Sai's combat abilities, enhanced by his mastery of Hasshoken and Haki, make him a formidable and versatile warrior.

Family

Chinjao

Sai cares deeply for his grandfather Chinjao. He was visibly upset when he couldn't get information about Chinjao's condition from the Colosseum's medical staff. Sai also acts as a guide for his grandfather, preventing him from clashing with Luffy and Cavendish and potentially ruining their mission.

Despite their occasional disagreements, there is a strong bond between them. Chinjao is proud of Sai's skills in the Hasshoken martial art, and after Sai's victory over an executive member of the Donquixote Pirates, Chinjao acknowledged that Sai had surpassed him. Their relationship is marked by mutual respect and admiration.

Boo

Sai shares a close brotherly bond with Boo. When Boo was defeated by the Funk Brothers, Sai's attachment to his brother was evident. Despite the Hasshoken training, which discourages deep emotional attachments during battle, Sai still cares deeply for Boo. He is willing to avenge his fallen comrades, including his brother. Boo also plays a guiding role for Sai, similar to the dynamic between Sai and Chinjao.

Baby 5

Sai's relationship with Baby 5 underwent significant changes. Initially, they were opponents at Dressrosa. However, Baby 5 fell in love with Sai and even contemplated suicide when he dismissed her. Sai intervened, defeating Lao G, and declared his intention to marry Baby 5.

This led to her elation, and she began affectionately calling him "darling." After breaking off an engagement with Uholisia, Sai officially married Baby 5, solidifying their relationship. Sai's love for Baby 5 is evident, and he appreciates her cooking, which is his favorite. Their marriage represents a significant development in Sai's character arc.

Enemies

Donquixote Doflamingo

Sai harbors a strong dislike for Doflamingo due to the Warlord's involvement in illegal arms trading and instigating wars in his country. Doflamingo's actions led to Sai's transformation into a toy and enslavement, intensifying his animosity. Sai is determined to stop Doflamingo's unlawful activities and seeks revenge for the suffering he endured.

Trebol and Sugar

Sai's encounter with Trebol and Sugar resulted in his abduction, hypnotization, and transformation into a toy. He was frustrated and dismayed by his lack of control over his own body as Trebol manipulated him. His experience with these two members of the Donquixote Pirates was distressing and dehumanizing.

Lao G

Lao G, as a member of the Donquixote Pirates, was an enemy to Sai and the gladiators who supported Luffy during the Birdcage game. Sai fought Lao G not only to assist Luffy but also to protect Baby 5 and avenge his grandfather's defeat. His conflict with Lao G was motivated by his loyalty to his allies and his desire for justice.

Allies

Monkey D. Luffy

Sai and Luffy initially crossed paths during a confrontation in the colosseum, where Sai defended Luffy from disqualification, and they shared a brief exchange of gratitude. Despite this initial encounter, Sai and Luffy did not form a close relationship at first. However, during the Birdcage incident, Sai and his family chose to ally with Luffy, supporting his pursuit of Doflamingo rather than going after the bounty on his head.

After Doflamingo's defeat, Sai and the other captains swore their loyalty to Luffy. This act of allegiance reflects Sai's recognition of Luffy's role in their victory and his willingness to serve under the Straw Hat captain.

Additionally, during the Levely, Sai and Leo proudly proclaimed their status as Luffy's subordinates after intervening in an altercation involving Charlos. This shows their continued loyalty to Luffy and his crew.

Ideo

Sai and Ideo share a mutual respect for each other as fighters, evident during their battle in C Block of the Corrida Colosseum. Their respect eventually leads to an alliance, as they both join forces to defeat the Donquixote Pirates and become members of the Straw Hat Grand Fleet.

Riku Doldo III

Initially, Sai held Riku Doldo III responsible for allowing Doflamingo to come to power. This blame likely stemmed from the suffering that Sai's people endured under Doflamingo's rule. However, Sai's opinion of Riku Doldo III may have mellowed after learning of the king's innocence in the matter.

Leo

Sai and Leo consider each other comrades and share a sense of camaraderie. When Leo attempted to rescue Shirahoshi from Charlos, Sai quickly came to his aid. They later cooperated again, with Saint Mjosgard's permission, to confront Charlos after the latter's second attempt to capture Shirahoshi.

Others

Funk Brothers

While Sai may not have significant qualms with the Funk Brothers outside of their Corrida Colosseum match, he did defeat them in battle with the specific intention of avenging his brother's defeat. This battle likely created a competitive but not necessarily hostile relationship between them.

Uholisia

Uholisia is Sai's former fiancée. She appeared eager to marry Sai and become his 26th wife. However, when Sai broke off their engagement, Uholisia's response was violent, as she angrily beat him up. This indicates a tumultuous and contentious relationship between Sai and Uholisia due to the broken engagement.

In addition to the manga and its anime adaptation, Sai also appeared in One Piece: Great Pirate Colosseum.

• Sai's birthday on August 13 may be a reference to his role as the 13th leader of the Happo Navy.

• His favorite food is bento from his wife, and his least favorite food is crab.