Sister, a God?

Yuki is Nanami's long lost younger half sister. Yuki is 15 and has been evicted as her mom and, both Nanami and her, dad left, Yuki has come to be with her sister. Strangely, they are in the same grade for Yuki excels in school. Kurama loves her, Tomoe likes her, but doesn't quite trust her, and Mizuki is scared of her.