SPOILER ALERT: the following article contains massive spoilers, including the ending. If you have not yet seen the movie, proceed at your own risk, or better, come back to this article later!
SPOILERS AHEAD
The Door into Summer Plot Summary and Synopsis
In 1995, Soichiro Takakura (Kento Yamazaki) is a scientist and works on developing a robot. He is also on the verge of completing a plasma storage battery, following on the wishes of the deceased Matsushita. The man Matsushita was a friend of Soichiro Takakura’s late father. Outside of work, Soichiro Takakura has peaceful days with his cat Pito and his fiancé Riko, who is the daughter of Matsushita. He is soon betrayed by his business partner and also by his fiance Riko. Soichiro Takakura loses control of his company and the work he has done on the robot and plasma storage battery. Soichiro Takakura then opts to place himself into a “cold sleep” freezing machine, hoping to find a better future. When he wakes up, he discovers that he is in the year 2025.
Source: Wikipedia (CC BY-SA 3.0).