Kazuki Kosuda

Kazuki Kosuda is Takashi's older sister and a college student.

Personality
Although she likes to tease her brother, she still deeply cares about him. She isn't shy about showing her naked body, for Takashi at least. She gives Takashi tips on his relationship with Yamada, too. She seems athletic, as she has been seen lifting weights, and has even rode a motorcycle.

Appearance
She has short dark red hair and brown eyes. She is really beautiful, as said by Yamada. She has very large breasts and a slender, yet curvy figure.