The compilation film will recap the anime's 59 episodes from seasons one to three.

Osamu and Youko Sonoyama want more than anything to adopt every child from Soramame House, but the wealthy couple can only pick one due to their increasingly old age. While they contemplate this delicate decision, one child's alluring beauty and gentle soul instantly draw them in. Two months later, the Sonoyamas welcome 13-year-old Hitori into their warm and loving home. However, Hitori's humble and overly polite exterior is merely a masquerade. In reality, Hitori is a carefully crafted character played by identical twins Migi and Dali. For them, being the ideal child of this kind couple is merely a stepping stone to infiltrating a certain quiet town. While dutifully protecting their cover, the twins work toward their true objective: to discover the truth behind a past incident that left them with a burning desire for vengeance.

In a fateful childhood encounter, Mira Kinohata met a stargazing dreamer named Ao Manaka. Though their time together was short, Ao showed Mira the wonders of astronomy, from orbiting planets to distant stars. Before they parted, Mira learned that a star with her name exists, but there are none with Ao's. And so, she forged a promise: one day, she would discover a new asteroid and name it after Ao. Years later, Mira is still fascinated with astronomy. Now in high school at Hoshizaki Academy, she tries to join the Astronomy Club. Unfortunately, she finds out that the club has been merged with the Geology Club to form a single Earth Sciences Club. She joins this new club and finds a pleasant surprise—she reunites with Ao after years of separation. Alongside their new clubmates, Mira and Ao begin their journey together to fulfill their promise. How hard could it possibly be to find an asteroid? [Written by MAL Rewrite]

Within the narrow walls of the Outdoor Activities Club room, the few but lively members carry on the camping spirit as they have fun with DIY club experiments. Exciting experiences such as these have brought Nadeshiko Kagamihara deep into the world of camping, making her want to once again go on a solo trip. However, other plans come first, as Ayano Toki and Rin Shima invite Nadeshiko to camp near Ooi River. Eager to go on their first journey together, the girls set off to forge precious memories that will stick with their hearts for years to come.