100-kai Mawatte Ai wo Nake

Iroha Shirobuchi, a poor girl on a scholarship, is just trying to get by and stay out of trouble. But one day, she accidentally falls down the stairs and lands on top of the school's biggest troublemaker, Kyogoku Matsuri. Matsuri, a wealthy playboy, wants her to become his “dog” as compensation…!?

(Source: Manga Park, translated)