Happy-Go-Lucky Days (どうにかなる日々, Dōnika Naru Hibi) is a Japanese manga series by Takako Shimura.

The manga is a collection of short episodes that depict slightly eccentric love stories and mundane daily life in a matter-of-fact manner with a unique tempo and delicate psychological descriptions.

[7] Although it has been almost 20 years since the manga's serialization, producer Yūsuke Terada thought that the "flat perspective on human relationships and love" of Shimura's work would be unique to today's age and planned the anime adaptation.

In selecting the episodes, since the maximum length of the movie was decided in advance, the concept was set to "a story that reminds us of someone who is no longer around us, but who was once close to us."

Initially, CreepHyp was only offered to compose background music for the film, but after reading the manga, Sekaikan Ozaki asked Terada if he could write a theme song as well.