LIttLE 13, LIttLE13 [リトルサーティーン]

After her mother passed away, a young girl named Pepe disguises herself as a boy in order to work. Keeping her mother's pendant with her, she travels to a secluded mansion to work as a servant. While working she stumbles across a secret passage leading her to a prison. Behind the prison bars is a man in a pig mask who calls himself Jack.