Yahiro has black hair and dark eyes, though both are often depicted in a light brown or gold color in some illustrations. He is normally shown wearing his Raira uniform, a black button-up blazer with a white undershirt complete with a black tie. His hair is a little messy, standing up a bit on top, and his bangs are swept out of his eyes, framing both sides of his face. His hands are noticeably scarred from constant fighting.
He is described as being an extremely cowardly individual, possessing twice the sensitivity to fear as the average person and detesting it twice as much as well. This causes him to have a somewhat paranoid personality and usually results in him going far overboard during fights, though he’ll be apologetic afterwards if he feels the individual didn’t deserve it. He doesn’t anger easily, usually only getting mad at people who have gone to extreme lengths to hurt either him or his family. Due to his situation, Yahiro seldom spoke with others outside of his family while he still lived in Akita; as a result, he’s not used to dealing with people and is rather timid and anxious around others, but he also tends to be very blunt and straight-faced about things a person ordinarily might not be. Honest to a fault, he's terrible at telling lies even when he tries, and he claims to avoid it because he’s afraid others will find out if he does.
Yahiro is an exceptionally strong fighter, even capable of holding his own against Shizuo Heiwajima. While his physical strength itself isn’t anything out of the ordinary, his prowess stems from his acute natural instincts and senses. Despite being a rather calm and timid individual normally, he has no sense of mercy or restraint once frightened. This frequently causes him to beat his opponents further than necessary, often striking them continuously even after incapacitating them. Even as a young child, Yahiro would show no hesitation in dealing vicious blows and targeting vital areas whenever he had been provoked.
After being repeatedly targeted by delinquents and people picking fights with him, Yahiro begins training in order to better defend himself. This on top of his already keen instincts and the experience that came as a result of his frequent fighting is what ultimately makes him so formidable. He believes violence is the only thing he’s good at.
Shortly after his birth, Yahiro was abandoned on the doorstep of a hot spring inn in rural Haburagi Village, Akita. The family of innkeepers - an old woman, along with her daughter and son-in-law - adopt and lovingly raise him. Due to the family’s high standing and wealth, however, some of the other children in the village grow envious of Yahiro's fortunate living conditions despite his lack of blood relations, and he becomes a target for bullying. When a boy grows angry and attempts to beat him, Yahiro becomes frightened and retaliates harshly, nearly (or possibly entirely) ripping the boy’s ear off and headbutting him without a moment’s hesitation. Even after the boy falls to the ground, Yahiro mercilessly continues kicking him in the face, not stopping even as he draws blood.
When another group of upperclassmen seek him out to avenge their friend, Yahiro responds with no less brutality than he had displayed to the previous bully and severely injures any who attack him. With his family’s influence, Yahiro is able to avoid any serious legal repercussions over the fights, but as a result, the rest of the village grows terrified of him. Believing his actions to be inhumane, they label him a monster and avoid contact with him.
While nobody else dares to attempt provoking Yahiro for a time after that, eventually those who had previously experienced his assaults begin spreading rumors of him in the nearby areas. By the time he enters middle school, delinquents from the surrounding regions are drawn by the rumors and desire to try their hand at fighting him themselves. As he is involved in more and more violent conflicts, word of his ability grows further, and his days become filled with endless fighting.
Terrified of the continuous hostility directed towards him and discouraged by his status as an outcast, Yahiro reaches a hopeless state by the time he turns fifteen and resigns himself to a meaningless existence as a monster. However, his life reaches a turning point when a tourist from Ikebukuro witnesses one of his brawls. Shocked that the man refers to him as a human even after seeing him fight and intrigued by his mention of other "monsters," Yahiro begins to research the city. He becomes fascinated with figures such as the Headless Rider and Shizuo Heiwajima and grows hopeful that the city might offer him a better chance at life. When the time comes for him to enter high school, he convinces his family to let him move to Ikebukuro and enrolls in Raira Academy.
After researching the city of Ikebukuro, Yahiro moves there and rents out an apartment from his relatives, the Togusa family. During the school introductions at Raira, Yahiro claims his reason for coming to the city was to see the Headless Rider which catches the attention of Himeka and Kuon. Himeka approaches Yahiro after school, warning him to stay away from the Headless Rider for his own good.
Kuon approaches Yahiro shortly afterwards in hopes of seeking out the Rider together, but Yahiro declines due to his previous conversation with Himeka. Kuon instead takes him to Rakuei Gym where they meet Mairu and Akane. They learn that one of Akane's seniors at school, Ai Tatsugami, is one of the recent victims pertaining to a case of multiple kidnappings effecting those who try to get close to the Headless Rider, but Akane asserts Celty's innocence in the matter. Yahiro becomes dejected as he realizes he was wanting to look at Celty in the same manner that others had seen him in attempt to feel more normal himself. He then offers to help Akane look for Ai in hopes of learning more of the Headless Rider's true nature.
Yahiro and Himeka meet up again the next day, and Yahiro explains to her his reasons for coming to Ikebukuro and seeking out the Headless Rider. Kuon shows up in search of Yahiro, and they learn that Ai is Himeka's younger sister and that her older sister, Aya, has gone missing as well. Himeka advises the two boys to refrain from searching into the matter for their own safety but lets them do as they please.
While Yahiro and Kuon are searching for information later that day, Shizuo overhears Kuon talking about how he had spread unsavory rumors of Celty's involvement in the case. When confronted, Kuon continues to enrage Shizuo and is flung through the air as a result. Before Shizuo can strike Kuon any further, Yahiro provokes Shizuo on his friend's behalf, picking a fight for the first time in his life. While Yahiro ultimately loses, he is able to knock Shizuo down several times and leave him with minor injuries. A recording of the fight makes its way to the internet, and while Yahiro remains anonymous to the general public due to the video's low resolution, Ikebukuro works itself into a buzz over the city's extraordinary newcomer.
Some time later while Yahiro, Himeka, and Kuon are out, Celty introduces herself to the trio and offers to help find Himeka's sisters in order to clear her name. Before the four of them can finish their conversation, however, Li-pei Ei approaches Yahiro after hearing about his match with Shizuo and provokes him in an attempt to test him. While Li-pei puts up a decent defense, it's short-lived, and Yahiro outmatches him. Before he is able to injure Li-pei further than necessary, Celty makes to stop Yahiro with her shadows, but he is able to dodge and backs away frightened. Kuon breaks Yahiro out of his fearful stupor, and Li-pei offers to lend a hand in the investigation should he find anything in return for a future favor from Yahiro and Celty.
When Kuon doesn't show up the next day for school, Yahiro grows concerned and questions Aoba about his whereabouts. Unaware of Kuon's situation himself, Aoba gives Yahiro Kuon's home address, and Yahiro and Himeka head there after school. They meet with no response when knocking at the door, but sensing that someone is inside despite that, they break in, fearing it may be the kidnappers and meet Kuon’s sister, Nozomi, who divulges that Kuon intentionally let himself be kidnapped and she goes on a bit about the siblings’ past.
After Himeka is kidnapped the same night, Aoba contacts Yahiro and offers to take him to where she and Kuon were being kept. On their way over, they happen across Celty who hears of the location from the Awakusu-Kai. Seeing Yahiro present, Celty pulls him aside and questions him on his motives for being there and in the city in general, fearing his ambitions may be similar to Mikado's in the past. Celty accepts Yahiro's reasons after hearing his explanation. She removes her helmet to encourage him, telling him even if he's a monster that he can still find others who accept him.
Following this, they both head into the villa and meet up with Kuon, Himeka, and Shiki who had already managed to free themselves. With Dragon Zombie, Jyan Jyaka Jyan, the Awakusu-Kai, and the group of kidnappers all causing chaos outside, they struggle to come up with a course of action until Yahiro volunteers to subdue them himself. Yahiro reflects on Celty’s words from earlier and follows her advice, deciding to willingly embrace the title of monster that has plagued him for so long. Overcome by the sense of release this brings him and clothed head-to-toe in her shadows, he finds that most of his fear has left him and he is able to fight with significantly more control. Yahiro single-handedly subdues the raging delinquents and the missing persons return home.
Footage of Yahiro's fighting once again makes it to the internet, and "Snake Hands," named so by Li-pei, effectively becomes Ikebukuro's newest urban legend.
Durarara!! SH x3Edit
After rumors of Snake Hands spread throughout the city, Kuon uses the opportunity to make an organization for freelance work under the same name. Yahiro and Himeka are recruited, as well as Celty. Yahiro takes up a job by Erika and Walker to find the suspect behind a recent chain of assault cases, also known as the Slugger. Aoba also tries to get Yahiro to find the suspect for the Blue Squares, and Yahiro becomes conflicted over who to bring the criminal to should he end up finding him. One night Yahiro meets up with Kadota's gang, and once they drop Walker and Erika off, Yoko (dressed up as The Slugger) targets him. Yahiro realizes either Walker or Erika would be targeted if they were to be alone, so Kadota and Yahiro run after Walker who is dealing with Yoko. When the real Slugger sneaks up behind Walker, ready to strike, Yahiro saves him by throwing his phone at an amazing speed at the hammer, changing the its direction.
- His name is based off of Hachiro-Taro, a character in Japanese tales.
- The ringtone of his cell phone is from the Carmilla Saizou movie franchise.
- He has admitted to being a fan of Ruri Hijiribe.