The story's protagonist, Narumi Takayuki is an ordinary high school student, neither especially ambitious nor stressed out about his college plans. He meets Suzumiya Haruka in a bookstore, one year before her best friend Hayase Mitsuki sets them up in their third year of high school. The relationship progresses at a snail's pace while he is unsure about his feelings, but Haruka gradually wins him over, even inspiring him to try for a tougher university. One day, while he is unexpectedly delayed by Mitsuki on her birthday, Haruka is involved in an accident as she waits for him at a busy transit station. During this time, Mitsuki takes care of him and the two become intimate and co-dependent, as they feel merciful and come to terms with Haruka's accident.