Youhei Sunohara (春原 陽平, Sunohara Yōhei?) is Tomoya Okazaki's friend and also a delinquent. He entered the Hikarizaka Private High School on an athletic recommendation in soccer, but was kicked out of the soccer club after being involved in a fight. After this incident, he became lazy, becoming the only student with a higher absence rate than Tomoya. He is left handed when it comes to sports and fighting (this is only mentioned in the anime), but he writes with his right hand, hinting that he is ambidextrous. He and Tomoya are known as the "Dirty Pair" in school. His hair is naturally black; he bleaches it blond. He has a younger sister named Mei Sunohara.
By ditching all the girls and getting a bad ending in the visual novel, Tomoya will confess his love to Sunohara.
Youhei is mostly a comic relief character; as a recurring gag, he often gets punished or beaten up by various characters due to his behavior, including Tomoya, but also noticeably Tomoyo and Kyou. Tomoya spends a lot of time with him in his room. However, Youhei plays minor roles in some of the character arcs, such as Fuuko's, when he helps her when everyone is starting to forget about her, or Nagisa's, during which he becomes a temporary member of the Drama Club. He is the one who comes up with the idea of challenging the basketball club to a match in order to get the Chorus club members to realize their determination after Yukine reads his fortune, and he plays with Tomoya and Kyou during the three-on-three match. As noticed by Tomoya, because of what happened to him in the past when he was kicked out of the soccer club, he hates people who use handicaps as excuses to get it their own way.
Youhei decides to aim for various girls during the series, but all of them end up rejecting him. This is portrayed as a comical situation.
During the first episodes Clannad ~After Story~, which are focused on the Sunohara siblings, Mei is worried about her brother. Thinking that he must find something to pretend he is happy with his life in order for Mei not to worry anymore, Youhei attempts to get a fake girlfriend, who finally turns out to be Sanae, who dresses up as a high school student. However, this turns out to be inefficient, and Mei starts thinking that he is not as dependable and strong as he used to be. Hoping that he will go back to being a good brother, she tries to pretend that she likes Tomoya, trying to get some response. However, Youhei makes no comments, but is obviously furious.
Youhei doesn't go to school for a while, and Nagisa, Tomoya and Mei go to the soccer club to beg to the members so they let Youhei rejoin, wanting him to have a goal in life. Even after being forced to do tedious tasks, they refuse to let Youhei come back and start bullying Mei. Youhei then storms in and, together with Tomoya, beats up the whole soccer club for bullying Mei. He then fights against Tomoya, revealing that he was worried about Mei all along. Nagisa and Mei intervene, and everything is solved. The next day, after seeing each other's swollen faces, they laugh and become good friends again.
Later in ~After Story~, he graduates along with Tomoya, and attends Nagisa's fake graduating ceremony in Graduation after being begged by Tomoya, and visits Nagisa when she is sick and pregnant. He is replaced by Akio Furukawa in his role as a comic relief character. Youhei starts working at a company as soon as he leaves high school. As seen in the episode Small Palms, it seems to be some kind of driving company.