Riko Morisawa, a young girl from Tokorozawa, travels to Tokyo with her friend Mana. While they walk through Ikebukuro"s streets, Riko sees a billboard advertising an event linked to the Little Battlers eXperience (LBX) toy line. Mana pushes her to buy a set, and although Riko hesitates at first, she eventually buys several LBX kits for her father. During their adventure, they also discover hidden stores that sell rare LBX parts.
When Riko opens a box marked "LBX Assassin," a temporal tear appears, pulling her into the sky of an alternate Japan. She falls at terminal speed, but a sleek exosuit—made from the same alloy as the LBX Assassin—materializes around her, saving her. On landing she encounters Mimesis, metallic creatures that invade worlds. While escaping these foes, Riko is rescued by four other girls armed with LBX gear. After learning of her situation, the group invites Riko to join their elite squad, "Soukou Musume."
The story of Soukou Musume Senki follows the unit as they face trials, forging unbreakable bonds and growing stronger together.
