Kekkaishi no Ichirinka

Eighteen-year-old Hana Ichise was born into the branch family of a long line of people with special abilities. Constantly compared to and overshadowed by her talented twin sister, one day, all of a sudden, a great power awakens within her. Hana, however, wanting to live a quiet life, hides her newfound power. Yet despite her best efforts, the young head of the main family, Saku Ichinomiya, discovers her secret and pressures her into marrying him.