Shigatsu ni nareba kanojo wa

Shun Fujishiro is a psychiatrist and works at a university hospital in Tokyo. He is engaged to Yayoi Sakamoto. One day in April, when he is about to marry Yayoi Sakamoto, he receives a letter from his first love Haru Iyoda. They dated 10 years ago. Suddenly, his fiancé Yayoi Sakamoto disappears.