Fireflies: River of Light (2004)

Wouldn't it be beautiful to see fireflies dancing here?

After finally passing his teacher's exam, Miwa (Yukiyoshi Ozawa) devoted himself to teaching in a rustic primary school. He struggles to get through to his students, until he creates a class project to raise fireflies to fly over it once again. All students, even the reserved girl Hikari (Risako Sugaya), become passionately involved in the project. However, it brings them into conflict with parents and the school, one problem after another stands in his way.