The movie takes its story from Taku Mayumura’s science fiction book Nerawareta Gakuen, which first came out in 1973 and has been reworked into TV shows and movies before this. The ideas about the future—like traveling through time and a changed Earth—are remarkable when you think about how old the original story is. It's really enjoyable to watch and listen to, with beautiful animation, intricate settings, and sound that fits well with what’s happening on screen. Still, the way the characters are developed isn’t consistent. The main ones have different personalities, but sometimes their feelings don't seem realistic or like they make sense. Seki’s part in the story doesn't feel fully explored and gets lost because of Ryoichi, which makes his quick development hard to believe. There are moments where the plot just jumps around—especially what happened with Yamagiwa, which isn't explained and led to the school's strict rules and had a big effect on important things that happen. The characters are meant to be middle school students, but they look and act more like older teenagers in their romantic scenes. Even though there are problems with it, the film does teach you something about understanding others and talking to them: truly getting someone else starts with being honest and open.

Source on TMDB