Maria†Holic

Kanako Miyamae transfers to Ame no Kisaki Catholic school, seeking a romantic partner like her parents had. However, because she breaks out in hives around men, Kanako ends up at the all-girls school to look for a female partner. There, she meets Mariya Shidou, who Kanako initially believes to be her perfect match. Unbeknownst to Kanako, Mariya is actually a cross-dressing boy who replaces her original roommate and forces her to keep his true gender a secret in exchange for not exposing her own intentions.