Savage Garden

In 18th century England, Gabriel, an orphan girl from a fallen noble family befriended a young man named Jeremy, who was rumored to be an illegitimate child of a nobleman. After an incident occurred, Gabriel must impersonate her friend Jeremy, taking his place at an all boys academy for nobles, a place that may seem like heaven to others, but really hides a harshness which she would never have imagined.
(Source: MangaUpdates)