Sota Mizushino, a high school anime fan, is pulled into the world of a mecha anime playing on his tablet and witnesses its protagonist, Selesia Upitiria, fighting a girl in military uniform. When both characters materialize in modern Tokyo, Sota learns that fictional characters from manga, anime, and games are crossing into reality. Some of them follow the military-uniform girl, Altair, who promises to reshape their home worlds. Sota and Selesia join the strategist Meteora to gather the scattered creations and stop Altair before her plan collapses the boundary between fiction and reality.