"A young teacher has some good ideas about teaching, but he finds himself up against Japan's regimented and conservative school system.
As a class project he decides to raise fireflies. Through the project his students become united and end up cleaning up a local river so the fireflies will have a home.
Based on a novel, "Hotaru no Hoshi" by Satoshi Muneda.
This novel is written based on the real story. " CrunchyRoll