Futami Sena

Likes: Being first in everything
Dislikes: Her stupid brother

Seiji's younger twin sister. They both have the same face, but their personalities are completely different. Sena is smart, not to mention her thought process is quick. However, she is a narcissist with the biggest pride out of the girls. She's also a mimidoshima (a person with lots of knowledge about sex) despite being a virgin.