Haruki Mishima and Towa Honda are new students at Aokisora High School and best friends; at a convenience store near their high school, Haruki runs into his classmate Miharu Mashiki, a girl he's recognized since he was little.

Haruki has been unable to focus during swim practcse since the new semester started; though his relationship with Miharu has returned to normal, he still feels as though something is lacking; Miharu begins missing school for some reason.