Tanikaze Amane

Riku's younger sister, who was also a demon in her past life.

She can be somewhat shy with strangers, but once you get to know her, she's actually a very lively girl.
And despite how bratty she can act toward Riku, overall they have a pretty good relationship.

She's also a huge gamer girl, and often stays up really late playing various online games.
Unfortunately, this tends to backfire on her the following morning.

From NekoNyan's official Twitter