Naked Prince(2007)

Hadaka no Oujisama ~ Love Kingdom ~

After both of her parents died, Nanako lived in a home/temple for orphans and helped out with the daily chores. One day she is told that she will become a student at a very elite and expensive high school! But how? Soon she is brought to a gorgeous mansion, where she is told she will be living from now on. There she encounters a very handsome guy named Subaru who claims she is his fiancee! (Source: Manga Abyss)