We Couldn't Become Adults

In WE COULDN'T BECOME ADULTS, Makoto Sato (Mirai Moriyama) is a 40-something man who works hard for little reward. One day, he receives a friend request from a girlfriend from many years ago. This message prompts Makoto to remember all his relationships, all the way back to his first real love, Kaori Kato (Sairi Ito). By the time he's done, will he know why he is still alone?