Young not stupid - Diabolik Lovers
Rito Komori, ah Komori, the same last name as Yui Komori.
Rito was adopted into the Komori family after she had dealt with a horrible family life.
Her "father" was a manipulative, cheating husband to a kind intelligent woman who had 4 children.
One of those children was Rito, she had 3 older brothers, but they had a different father.
Rito's father had manipulated the girls mind from a young age, but she however broke from his control and matured mentally quick.
Her mother would often tell her she was a 19 year old in a 7 year olds body.
When Rito's father lost a gamble, he sold his wife and Rito's half brother away and they were eventually killed.
Social workers took Rito away from her "father" and gave her to a local church where she spent the next 5 years with Yui and Seiji Komori.
Yui was a dense spoiled brat, and Seiji barley paid the 12 year old any mind.
Now Yui and Rito are going to live with distan relatives of Yui's and Seiji's.
"Young, yes. Stupid, no"
(Just a warning, Yui's a..yea, she's a b*tch, so if you like Yui, please try and hold back on your hate for me since the later chapters are about healing the bond between Yui and Rito)