Oniisan, a typical salaryman, has the weekly duty of protecting high school student Ai-chan from gropers by escorting her during their Monday morning train commutes. Despite the short time Oniisan and Ai-chan spend together, they manage to bond and learn more about each other's lives. To help Oniisan get through his Monday blues, Ai-chan gives him small presents as motivation.

Ai-chan and many other girls—who all share a certain attractive trait—lighten up the Mondays of their male friends and colleagues for the long week ahead.

[Written by MAL Rewrite]