Clannad - Season 2 Episode 7 Where She Belongs

Tomoya, Nagisa, and Youhei finally find out that Yukine is respected by the two rival gangs in the city since she helps both sides' members after they get hurt. Her older brother is the leader of one of the gangs, and a young boy named Yu comes to her to find his older sister who apparently is dating a guy in Yukine's brother's gang. Youhei tells Yu that he is Yukine's brother for a time, but the truth is later revealed after Yukine takes Yu, along with Tomoya, Nagisa, and Youhei, to a bar where her brother's gang hangs out. Yukine's brother has been in the hospital since he saved a friend and got in a car accident. While heading home, three members of the rival gang think Youhei is Yukine's brother and try to fight him and Tomoya, but Tomoyo intervenes, stopping them single-handedly.