Yashio is a debt collector who one day ends up saving a girl called Mikumo from a car accident. Mikumo, wanting to repay his service to her, decides to help him out with his job. Yashio refuses at first and tells her to get lost, but he eventually accepts and a new combination pair is born. But these two aren't ordinary or even human; They are in fact cats from the hidden cat society!?
Extra story: Kare to Kanojo no Futomin (volume 1)