Yotsuya Tomosuke (voiced by Uemura Yuto) is a third-year junior high school boy. In the class, Tomosuke is an unknown student. He doesn't like to make friends, and he is mediocre in his studies. He always keeps to himself. One day after school, Tomosuke accidentally traveled to a different world. To his shock, he met his classmates Shindo Iu (voiced by Kubota Risa) and Hakozaki Kusue (voiced by Kazumi Kazumi). One of them is a very popular beautiful girl in the class, and the other is weak and sick, always on sick leave. However, in this world, the three of them are partners fighting side by side. This is not a peaceful world. Tomosuke and his group have to fight against enemies who are much stronger than them. In order to win and save their lives, everything has the value of being used, even the lives of their companions, which can be used as chess pieces to play games with opponents.