When Dazai and Chuuya were little kids, 10 years old at the same elementary school, Dazai told Chuuya that he'd marry him one day. Now those promises happen with kids all the time, but it never happens since they're too young to understand what marriage means.

When the school heard about it, they told Dazai's mother, she was furious and pulled Dazai out of school, soon they moved away, leaving Chuuya without his best friend.

12 years later, that promise still stands, and Chuuya only hopes.