GLO-RI-A ~Kindan no Ketsuzoku~

You are Kira Akishino, an ace student from one of the best universities in Boston. You are offered a tutoring job at the illustrious Gloria mansion, along with your friend Georg. The Gloria family has long been one of the wealthiest and most prominent empires, and they need you and Georg to tutor one of the five daughters. Georg is immediately taken with the eldest daughter -- the strong-willed Etana Gloria, which leaves you with four others to choose from. There's Sicile, who has the worst grades of them all; Mary, the naive golden-haired angel; Naomi, who cares about nothing else but drinking; and Charme, the most brilliant one of the Glorias. But there's something more to it all... the Glorias are hiding some things, and it's up to you to find out what they are. Will you be able unlock the family secrets? Or will you just be a good tutor? Who knows, you may even end up marrying one of the Glorias...

[From Animetric.com]