Hikari

When Nobuyuki was a middle school student, he lived on the remote island of Mihama. One evening, he committed a crime to protect his classmate/girlfriend Mika. The next day, a fierce tsunami struck the island. Nobuyuki, Mika, and their friend Tasuku, along with several adults, survived. 25 years later, Tasuku appears in front of Nobuyuki, who is now married to Namiko and has one child.
~~ Adapted from the novel "Hikari" by Miura Shion.