Hana to Shinobi

Benio is the heiress of the richest family in Japan, and tradition holds that she must marry the first person to kiss her. So that she can attend high school, Benio is assigned the ninja Tamaki as a bodyguard, but he turns out to be quite the player. It's not always easy for a strong-willed rich girl and a smart-alecky ninja to get along in this romantic comedy about a pure young lady and her smoking-hot knight.
(Source: Kodansha USA)