Ai da to ka Fukushuu da to ka

One day, Kaede Koshiba's day began with a strange feeling. As her family and classmates tell her things that she does not remember, Kaede realizes that she 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 her, an incident occurs that changes Kaede and Yuka's daily life.