音無奈緒子

She is the daughter of the next-door neighbor and a female college student. She is asked to take care of the Akira and his friends but she just ends up causing a mess. She is crass and masculine, and her words and actions are rough. She still treats Akira as a kid. She is not good at housework and usually leaves it to her older sister, Kikuko. She has a bad drinking habit, and when she gets drunk, she gets unusually excited. [From official site]