Ai da to ka Fukushū da to ka

One day, Kaede Koshiba's day began with a strange feeling. As his family and classmates tell his things that he does not remember, Kaede realizes that he is being replaced "every other day" by a strange girl named Yuka Tsutsumi. Just as Kaede tries to solve the strange phenomenon that suddenly happens to him, an incident occurs that changes Kaede and Yuka's daily life.