When Shiro was a student, Yumi divorced her husband and raised Shiro on her own. She managed to get Shiro into college, but Shiro couldn't get used to college and dropped out. Since then, Shiro, who has no motivation to do anything, earns daily money with a popular home delivery service using the Internet. Yumi invited Shiro to a hot spring trip, saying that he couldn't stay like this.
