Gapz Garden(2003)

Koshien

This young girl is often mistreated by her family, being called ugly and useless. One day, she meets the new wife of the Yee family, which changes her life forever. The woman adopts her into her wealthy family, and now she lives with 3 other boys around her age. But for what purpose? Even though this is a miracle, the girl plans to leave the luxurious lifestyle once she turns 18. So see how she survives more than 10 years of her life.

(source: MangaJouhou)