Toshi, your ordinary high school student, spends his days being fed and taught by a beautiful neighbor named Yuu-neesan, who lives near his house instead of his parents, who were rarely home. The older sister was kind and perfect as an adult. However, she has a secret. when she plays games, she becomes a totally different person...!? She's not playing around! She rages, strips, and does whatever it takes to win! Toshi can't handle her split personality! It's gaming time with Onee-chan, and things are about to get wild!