Ii Ko no Ura Jijou

This is a love battle between Tsui, the mayor's daughter, and Shiro, the heir of a yakuza clan. Although Tsui has regarded Shiro as her rival since childhood, she has never been able to beat him in either sports or academics, always coming in second place. However, the relationship between the two changes as they play a game in which the loser must obey the winner. (Source: Natalie, translated)