Kana Tatebayashi 館林火奈

Kana is a half-mermaid half-vampire youkai. She 5 years old and is under the care of Shidou after their parents got tuned in an incident not long after they were born. Unlike her twin Mina, her blood is closer to a vampire's, and her body grows into a teenager size (with huge boobs, unlike Mina) if she drinks blood. Another difference is that she is soft-spoken and is always apologetic for Mina's rudeness.