Clannad: After Story

Synopsis

Mei has become worried about her older brother Youhei since he still does not have a plan after high school, and comes to stay at Nagisa's for the time being. Based on a fleeting comment by Youhei, Tomoya gets the idea to ask a girl to pose as his girlfriend so Mei will stop worrying about him. Youhei goes around with Tomoya and Nagisa asking Kotomi, Tomoyo, Ryou Fujibayashi, and Yukine Miyazawa, but no one can help him. Sanae Furukawa overhears Youhei's trouble and decides to be his fake girlfriend if it will help push him in the right direction in life. Youhei, however, still believes her to be the older sister, instead of the mother, of Nagisa. When Mei meets her brother's so-called girlfriend, Sanae is posing as a student from Tomoya's high school. (Source: Wikipedia)