Enoshima Prizm (2013) on Netflix

Plot summary

Shuta, Saku and Michiru have grown up together, and as children they carried Saku, who has a weak heart, up a hill where the three of them saw a rainbow. Michiru decides to study in England. She cannot say it to their faces, so she writes a letter and asks Shuta to give it to Saku on the day she leaves, December 21, 2010. That day Saku dies on his way to the station to watch her leave, and Shuta blames himself. Shuta and Michiru lose contact. On the anniversary of the death, Shuta is given a memento: Saku's watch, which is said to be able to rewind time. He puts it on, boards a train, and steps off on December 20, 2010, the day before Saku dies.