Onimaru in One Piece

Onimaru served as the companion of Ringo's daimyo, Shimotsuki Ushimaru until Ushimaru was killed in a rebellion against Kurozumi Orochi and Kaido about 18 years ago. Despite the devastation that turned Ringo into a wasteland, Onimaru remained around the main cemetery for about five years, protecting it from robbers.

Thirteen years before the present day, Onimaru encountered the samurai Kawamatsu while chasing away members of the Beasts Pirates. Despite initial opposition, Kawamatsu and Onimaru formed an alliance to collect weapons from the graves for a planned final battle against Orochi and Kaido.

However, when Kawamatsu was captured less than a year later, Onimaru continued the mission alone. Taking on the alias "Gyukimaru," he stole weapons from anyone crossing Oihagi Bridge and stored them in an underground chamber.

Wano Country Arc

Gyukimaru, posing as a human, was in Ebisu Town when he took the sword Shusui. He returned it to the grave of Shimotsuki Ryuma in Ringo. Later, on Oihagi Bridge, he confronted Roronoa Zoro, who wanted to reclaim Shusui.

They battled, and Gyukimaru attempted to take Zoro's other two swords. During the fight, a woman and a girl being chased by Kamazo appeared. After Zoro defeated Kamazo, Gyukimaru took the assassin's scythe and left as Zoro fainted.

Two days later, Zoro confronted Gyukimaru again, determined to reclaim Shusui. Kawamatsu interrupted the fight, and Gyukimaru was attacked by Beasts Pirates seeking revenge. As Zoro and Kawamatsu fought the Beasts Pirates, Gyukimaru fled with tears of joy upon learning that Kawamatsu was alive.

He led Zoro to the main cemetery, where he revealed the secret room storing all the weapons. Gyukimaru then transformed back into Onimaru. Later, after the Raid on Onigashima, he reunited with Kawamatsu in Ringo.

Onimaru is fiercely protective of the graves in Ringo, dedicating almost two decades to safeguarding them, enduring injuries in the process.

He is violent against those who try to violate the graves, relenting only when Kawamatsu offers his arm to take weapons. As Gyukimaru, he was sceptical of Zoro's claim about Shusui and showed little interest beyond guarding graves and stealing weapons.

In his Gyukimaru form, Onimaru displays intelligence and awareness of Wano's legends and history. He reveres the legends of Ryuma and goes to great lengths to return Shusui to his grave. In battle, he is pragmatic, always seeking openings, even against distracted opponents. Despite his violence, he refrains from attacking opponents who can no longer fight.

Onimaru, as a komagitsune, strongly resembles a fox with flaming fur, a swirly appearance on his pointy ears, and a large, fiery tail. He is sizable, being over half the size of the large kappa Kawamatsu.

In his Gyukimaru form, he transforms into a large man with a mask-like face. He wears a dark kimono, light pants, a large bead necklace, and a light cape, carrying numerous weapons on his back.

Onimaru is a skilled thief, capable of successfully stealing Shusui and traversing Wano Country swiftly. He has a powerful jaw, causing considerable injury to Kawamatsu's arm with a bite, impressive endurance, enduring arrows, and a bazooka shot from the Beasts Pirates.

As Gyukimaru, he exhibits remarkable skill with a naginata, clashing evenly with Roronoa Zoro and countering sword strikes with the staff handle. Gyukimaru wields a very long naginata and carries a variety of weapons on his back.

Onimaru ate the Hito Hito no Mi, Model: Onyudo, a Mythical Zoan-type Devil Fruit allowing him to transform into a full monk yokai and a komagitsune-monk hybrid. In his Gyukimaru form, he has enormous strength, matching Zoro's power, and great speed, able to keep up with Zoro's agility.

• Komakitsune or Komagitsune (狛狐) is a type of Komainu, which are foxes placed in Inari shrines associated with fox deities or spirits.

• Onimaru and his Gyukimaru transformation might be inspired by Benkei, a Japanese warrior monk who took weapons from defeated samurai. Benkei later became the loyal retainer of Minamoto no Yoshitsune, whose childhood name, Ushiwakamaru, may have influenced Shimotsuki Ushimaru's name.

• Onimaru's name may derive from Benkei's childhood name, Oniwaka (demon/ogre child), or Oniwakamaru. It could also be linked to Onimaru, a sword in Japanese folklore that moved by itself and defeated a cursed oni.

• "Gyukimaru" likely combines his former master Ushimaru's name and his own, as Gyūki is another pronunciation for ushi-oni. His transformation into Gyukimaru may draw inspiration from the shape-shifting abilities of fox spirits in Japanese folklore.

• Onimaru shares similarities with Chouchou, both being canines that were once companions of now-deceased men. After their companions' passing, they dedicate their lives to protecting the locations once controlled by their companions from criminals.

• Coincidentally, the joruri and kabuki play "Yoshitsune and the Thousand Cherry Trees" features Genkurō, a kitsune who disguises himself as the retainer of Minamoto no Yoshitsune.

• Onimaru's favorite food is abura-age.