After the death of his master, he joined forces with Kawamatsu in protecting Ringo's graves from robbers. After Kawamatsu was captured, Onimaru posed as a human known as Gyukimaru on Oihagi Bridge, stealing weapons from people while continuing to guard the graves.
Being a komakitsune, Onimaru heavily resembles a fox, with his fur and tail having a flaming composition, and his pointy ears have a swirly appearance. His fur is light, with his legs being dark below the knees. He is rather large, appearing to be over half the size of the very large kappa Kawamatsu.
As Gyukimaru, he is a very large man with a face resembling a mask. He wears a dark kimono, light pants, and a light cape, and carries many weapons on his back. He also wears a very large bead necklace.
Onimaru is fiercely protective of the graves of those buried in Ringo, and has tirelessly worked to protect them for almost two decades, enduring multiple injuries in the process but never wavering. He is very violent against those who try to violate the graves, as shown when he kept biting Kawamatsu's arm despite the samurai's pleas. It was only when Kawamatsu offered Onimaru his arm to show that he had not come for personal gain that Onimaru let him take the weapons from the graves. As Gyukimaru, he was unwilling to believe Roronoa Zoro's claim that he had rightfully obtained Shusui from Ryuma. He does not seem to take much interest in activities outside of guarding the graves and stealing weapons from passersby, as he stood and watched when Zoro protected Kozuki Hiyori and Toko from Kamazo.
Onimaru has shown in his Gyukimaru transformation that he is very intelligent and aware of the legends and history of Wano. This is seen as he greatly reveres the legends of Ryuma, and so went to great lengths to return Shusui to his grave, as he left Ringo and went to Ebisu Town near the Flower Capital just to take it back. He is rather pragmatic in battle and always looks for an opening on his opponent, even when they are distracted or caught up by something else altogether. However, he would not attack an opponent who can no longer fight as he left Zoro alone when he fell unconscious from a wound he received from Kamazo.
Abilities and Powers
Onimaru is a skilled thief, being able to successfully steal Shusui from Zoro and make his way halfway across Wano Country at a fast pace.
His jaw is quite strong, as he was able to instantly cause considerable injury to Kawamatsu's arm by biting it. He also has considerable endurance, as he stood to protect the graves after being struck by arrows, and in the present day, he was able to withstand a bazooka shot from one of the Beasts Pirates.
Through currently unknown means, Onimaru is able to transform into a large humanoid, who is known as Gyukimaru. As Gyukimaru, he is capable of human speech.
Befitting his size, Gyukimaru has enormous strength as he could easily match Zoro's physical power. He also has great speed, able to match Zoro's agility, though in their next match, he was easily overwhelmed by Zoro, implying their first match was because he caught the swordsman off-guard.
Gyukimaru has shown to be extremely skilled in wielding his naginata, able to clash evenly with the extremely powerful swordsman Roronoa Zoro. He has been shown using the handle of the staff to counter Zoro's sword strikes.
While acting as Gyukimaru, his main weapon is a very long naginata, which grants him great size and range in addition to cutting power. He also carries around a very large variety of weapons on his back.
Onimaru served as the companion of the daimyo of Ringo, Shimotsuki Ushimaru, until around 18 years ago when Ushimaru was slain in rebellion against Kurozumi Orochi. For around five years, he remained around the region's main cemetery, protecting it from robbers even as Orochi and Kaido turned Ringo into a wasteland.
13 years before the present day, Onimaru was chasing away some members of the Beasts Pirates when he encountered the samurai Kawamatsu. He collapsed from receiving multiple wounds, and Kawamatsu nursed him back to health. After regaining his strength, Onimaru opposed Kawamatsu's effort to collect the weapons of the buried, and bit into his arm. Kawamatsu revealed that he wished to collect the weapons for a planned final battle against Orochi and Kaido, but Onimaru did not budge. However, he relented when Kawamatsu offered him his arm, and licked away the blood from the wound he dealt. Onimaru then assisted Kawamatsu in collecting the weapons, and Kawamatsu aided him in protecting the graves from robbers, disguising himself as "Gyukimaru" when chasing them away.
Less than a year later, Kawamatsu was captured during a trip to the Flower Capital, leaving Onimaru alone again. As 13 years passed, Onimaru appeared to people as a human, donning Kawamatsu's alias of Gyukimaru. As Gyukimaru, he ambushed anyone who crossed Oihagi Bridge and stole their weapons, and stored all of them in an underground chamber.
Wano Country Arc
Gyukimaru was in Ebisu Town when he spotted the sword Shusui and took it. He went to Ringo and returned it to Ryuma's grave before he was confronted on Oihagi Bridge by Roronoa Zoro, from whom he had taken Shusui. Refusing to believe Zoro rightfully earned the sword, Gyukimaru battled him to take his other two swords. A woman and a girl then came onto the scene being chased by Kamazo, and as Zoro turned his attention to Kamazo, Gyukimaru repeatedly tried striking at his openings, annoying the swordsman. After Zoro defeated Kamazo, Gyukimaru took the assassin's scythe and walked away as Zoro fainted from the wound he received from the assassin.
Later, Gyukimaru was once again confronted by Zoro, who was determined to take back Shusui. Kawamatsu then came and interrupted the fight, and Gyukimaru was attacked by some Beasts Pirates who came seeking revenge on him for stealing their weapons. As Kawamatsu and Zoro fought the Beasts Pirates, Gyukimaru fled with tears of joy from learning that Kawamatsu was alive. After watching Kawamatsu's group go into the room where he stored all the weapons, Gyukimaru transformed back into Onimaru.
- Onimaru and his Gyukimaru transformation are possibly based on Benkei, a Japanese warrior monk who was said to have stolen weapons from samurai that he believed to be arrogant and unworthy.
- Onimaru's name may be based on Oniwaka (鬼若 demon/ogre child?) or Oniwakamaru, Benkei's childhood name.
- "Gyukimaru" is a combination of the names of Onimaru and his former master Ushimaru, as Gyūki (牛鬼? "ox demon/ogre") is another pronunciation for ushi-oni. This portmanteau may be based on Ushiwakamaru (牛若丸?), the childhood name of Minamoto no Yoshitsune whom Benkei faithfully served as retainer.
- One Piece Manga — Vol. 93 Chapter 936 (p. 16-17), Onimaru makes his debut as Gyukimaru.
- One Piece Manga — Vol. 93 Chapter 938 (p. 12), Hiyori talks about Gyukimaru.
- One Piece Manga — Vol. 93 Chapter 937 (p. 6), Gyukimaru is introduced.
- One Piece Manga — Vol. 94 Chapter 953, Onimaru's true identity is revealed.
- One Piece Manga — Vol. 93 Chapter 937 (p. 6-9).
- One Piece Manga — Vol. 93 Chapter 938 (p. 2-3), Gyukimaru walks away as Zoro faints.
- One Piece Manga — Vol. 94 Chapter 952 (p. 2-4,14-17).
- One Piece Manga — Vol. 93 Chapter 935 (p. 11).
- One Piece Manga — Vol. 93 Chapter 937 (p. 6-9, 11-15).