A seemingly ordinary boy named Sōya Kuroi gets caught up in a conflict between seven heroes and a group of extraterrestrial creatures. Sōya, who lives with a talking cat-like creature and a maid, discovers he's an unwitting pawn in an interstellar war when the heroes, who are also powerful weapons, begin fighting the creatures. He's forced to fight alongside the creatures against the heroes, discovering his own hidden abilities in the process.
