Ayato is a part time worker who lives alone, struggling to survive. One day, his mother suddenly appears only to leave his young sister under his care. Ayato then goes to City Hall to ask for help, as he wants to leave his sister in a nursery school while he works. At that place, the one who had to help Ayato was Haruna, a serious and hard-working employee, but instead of listening to him and without knowing about Ayato's circumstances, began to preach saying "Even stray cats are more responsible with their children than you are." Ayato snapped saying "What do you know about me?"

A hard working employee and a hard worker who is underemployed, gradually heal each other's past wounds and become fascinated with each other. What kind of promise will these two people make when they have experienced hard times in the past? Can they trust in each other?