Nakahara Yusuke is a high school boy who has a very loving younger sister, Maria. She loves spending each day taking care of him, doing things such as cooking and cleaning around the house. However, she typically goes a bit too far into treating him like a child–she has a habit of coming to his classroom at lunch to hand-feed him his bento, or brushing his teeth for him at home. She even snoops out his hidden porn magazines. Other people think they're a bit weird, and that Maria acts like his lover or his mom.