Kiyoku Tadashiku Utsukushiku

A sole omega was born into an alpha family. They hid him away and raised him in secret, ashamed of his existence. Chikage (omega) is named heir of the Souma clan after his older sister ran away, the first omega to be the leader of an alpha-only clan. Hiroto (alpha) met Chikage once when they were both kids. They met again when Hiroto is chosen to take care of Chikage at school. But he's nothing like the sweet child who clung to him before, Chikage now has a cold attitude but a slutty body... and wants nothing to do Hiroto?!

Note: Includes one extra chapter.