Minato is a boy who stopped playing water polo due to a certain incident in the winter of his third middle school year. He picks the sport back up again with a new team when he starts in high school, but the fledgling team runs into many problems.
Rilakkuma, Korilakkuma, Kiiroitori, and Kaoru are off on an adventure to the theme park, but with closing time imminent it leads to a series of fun mishaps and incidents as the group squeeze a day of fun into tiny amount of time.
Kaoru's unexpected new roommate is Rilakkuma, a bear with a zipper on its back that spends each day just lazing around -- but is impossible to hate.