Blue Gateway of Happiness (2012)

Shigeru is the proprietor of a dried fish stand on Enoshima Island. His wife passed away several years before, leaving him to raise their two sons by himself. The older son, Masami, begins learning the family business, while the younger son, Jun, moves out of the house so he can live on his own. It turns out that when Masami and Jun were younger, they overheard a relative ask their father at their mother's funeral, 'Are you really going to raise someone else's child?' Ever since that day, both boys secretly feared they were the adopted child, and their relationship became increasingly strained. When Shigeru passes away, Jun returns for the funeral and demands that Masami tell him the truth about which one was adopted.