Youhei's younger sister, Mei Sunohara, lives in the rural countryside around Hikarizaka. She loves her brother dearly, and consistently worries about him. She visits her brother twice in the series, and works both times to make her brother more responsible. Her most prominent appearance is during the siblings' arc, leading Sanae to pose as Youhei's girlfriend. Though Youhei feigns annoyance with Mei, he cares for her. The two siblings eventually grow closer as a result of the arc; Youhei stands up for her when she is bullied by the Soccer Club.