Ayato is a part time worker who lives alone, struggling to survive in an unfavorable environment. One day, his mother suddenly appears only to leave his young sister under his care. Then Ayato goes to City Hall to ask for help, he wants to leave his sister in a nursery school while he works. In 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 out 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? 不遇な環境でひとり生きてきたフリーターの絢斗（あやと）。 ある日突然、音信不通だった母親から幼い妹を預けられる。 市役所に保育園の相談に行った絢斗の前に現れたのは、真面目で堅物の職員・榛名（はるな）。絢斗の事情を知らない榛名は「責任もって子育てできないなんて野良猫以下だ」と説教を始める。「てめえがオレの何を知ってるんだよ」と逆上する絢斗だったが……？ 堅物公務員×苦労人フリーター。最悪の出会いから徐々に互いの過去の傷を癒し、魅かれ合っていく。人を信じることに臆病になっていた二人が交わす約束のゆびきりとは？