With summer vacation coming to an end, the girls are having as much fun as they can with their remaining time. However, their daily shenanigans are cut short when Suguru Koshigaya wins the grand prize of a lottery—tickets to Okinawa! After hasty preparations, the Asahigaoka group embarks on a three-day trip for their final summer getaway.

Upon arriving in Okinawa and checking into an inn, the group comes across Aoi Niizato—the young daughter of the inn's hostess. Despite being of similar age, her mature demeanor leaves Natsumi Koshigaya reflecting upon her own childish nature. With the sign of an unexpected friendship blooming on the horizon, the girls waste no time diving into their ambitious sightseeing plans and regional activities!