On april 10th, after the last day of spring vacation, itsuka shidou started his school day. as he was woken up by his sister, he thought it would be a typical day. however, without warning, the town disappeared in an instant, leaving only a crater on the street where the mysterious girl stood. she asked him if he had come to kill her too. the girl is a monster of unknown origin and has been rejected by society. there are two ways to stop her: destruction or conversation. shidou's sister kotori suggested that he date the girl and make the spirit fall for him.