6th grader Haruto Nagino is the son of an inn owner in Hakone, a town that is famous for hosting the annual [Hakone Ekiden](https://en.wikipedia.org/wiki/Hakone_Ekiden). His daily mundane life suddenly changes after the arrival of a transfer student named Kanata Sakuraba. She is a weird girl that likes to "chase people's back" and somehow Haruto can't take his eyes off her.