Hadaka no Oujisama - Love Kingdom

Nanako lost her parents at a young age–she never knew her father, and her mother died right after she entered middle school. Since then, she has lived in a temple with other orphan kids. But Nanako always had the assistance of her father's old friend Seitou. One day, Seitou transfers Nanako to a luxurious school in Tokyo. There, a boy named Subaru kisses her, and it turns out that he is actually her fiancée.