Youhei is the best friend and classmate of Tomoya and a fellow delinquent. He is wild, energetic, and very random. Youhei's hometown is Honshu and he stays at a dormitory. Misae is the landlady of the dormitory and she dislikes Youhei for being messy and noisy. Youhei left his younger sister Mei behind and she wonders about Youhei's well-being. Youhei proved to be very protective of Mei.
Youhei developed a morbid fear of Tomoyo. He also became the punching bag for Tomoya, Tomoyo, Misae, and Kyou. Despite all the physical harm that Youhei receives, he manages to recover rather quickly. Youhei's hair was originally black but he had bleached it blond, which further propelled his image as a delinquent.
Youhei loves the song Bomb A Head, a hip-hop song produced by m.c.A.T. which is used as the opening theme of the Tenjou Tenge anime.
Back at home, Youhei had a reputation for being a mischievous boy. Mei would be bullied by the boys who disliked Youhei and Youhei would come to help Mei.
Youhei was recommended to the school based on athletic excellence, as he was a skilled soccer player. As time went by, Youhei lost his motivation in playing soccer and he was involved in a fight against a rival school's soccer team. Youhei was kicked out of the soccer team and he became lazy.
Koumura, Youhei's and Tomoya's first year homeroom teacher, noted that they were quite similar and he had Tomoya befriend Youhei. Tomoya saw Youhei's injuries and he laughed at him. Youhei also found his injuries funny and laughed along. From then on, Youhei enjoyed fooling around with Tomoya.
Youhei is Tomoya's inseparable friend and Tomoya often hangs out at Youhei's dorm room. Their homeroom teacher noted that their attendance rates were very poor. Youhei borrowed a television and VCR player from a friend and discovered that all his tapes were of comedy. He later borrowed a game console from a friend and discovered that all the games were educational games.
Sunohara Siblings' path
On April 23rd, Misae reported to Tomoya that Youhei's sister, Mei, is calling for him. If Tomoya took the phone, Mei announced that she will visit Youhei. Youhei revealed that Mei had been worrying about him. Youhei wanted to appear to Mei that he has a different dream and Tomoya suggested getting a girl to pretend to be his girlfriend. They couldn't get a girl to co-operate. At the park, they met Sanae, Nagisa's mother. Tomoya explained Youhei's situation and she volunteered. Youhei assumed that she was Nagisa's sister. Tomoya decided to keep the truth to himself.
That Saturday, Tomoya tried to dissuade Sanae from playing along but Sanae persisted. Tomoya became jealous. He went to Youhei's dorm room and greeted Mei. Youhei went on a date with Sanae. The next day, Tomoya and Mei met Youhei and Sanae at the park again. Youhei invited Sanae for lunch and revealed his poor diet. Sanae cooked lunch for them instead. That evening, Youhei invited Sanae to town and they saw a group of boys bullying a girl. Youhei wanted to ignore them but Sanae insisted on helping her.
Mei was sad to see Youhei change and Tomoya confessed that Sanae wasn't his girlfriend. The following day, Tomoya and Mei went to town together. When they returned, Youhei witnessed Mei kissing Tomoya on the cheek. Tomoya pretended to be her boyfriend and Youhei became angry but he didn't say anything.
On Thursday, Mei was begging the soccer club members to accept Youhei back to their club. They treated Mei badly and Youhei came to her rescue. He and Tomoya fought against the soccer club members but were beaten up. Tomoya yelled at Youhei for not protecting Mei but Youhei was fine about Tomoya being Mei's boyfriend. Youhei then yelled at Tomoya for making Mei go too far.
Tomoya and Youhei made up and became friends again. Mei was happy that Youhei was enjoying his school life and returned home. Youhei then requested Tomoya to bring him to meet Sanae. They visited the Furukawa bakery and they discovered Sanae's husband Akio.
If Tomoya meets but rejects all girls, he decided that he liked Youhei, much to his dismay.
Tomoya phoned Youhei and Youhei revealed that he was currently working and that he was staying at the company's dormitory. Tomoya invited Youhei to attend Nagisa's mock graduation party.
On January 3rd, Youhei, Nishina, and Sugisaka visited Tomoya and Nagisa. Youhei was surprised to see Nagisa pregnant.
- Tenjou Tenge first aired on April 1st, 2004 and the Clannad visual novel was first released on April 28th, 2004. Bomb A Head itself was first released in 1993. The song was re-released as Bomb A Head! Returns! in 2003, the year in which Clannad was set.