Wataru Morishita attends Osei Gakuen, which is based on academic ability. During the same lunch break as usual Wataru is deeply depressed when he receives a report of his marriage from his deputy homeroom teacher, Miwa Shirakawa, who was secretly thinking about it. At that time, an alarm sound is heard from the smartphone in the pocket, and the mysterious app Sai * app is displayed on the screen. Wataru gets an app that has a powerful effect, and Kyoko Tsukishima, who is in charge, is involved in making it into a female dog guy ○ ...