Abel and crew (Devil Survivor) must fight the Waves to prevent damage to their home colony in the Expanse. So, they summon people to become the Vassal Heroes. Hikaru (Rayearth), Takato and Guilmon (Digimon Tamers), Sinon (SAO), and Megumin (Kono Suba) answer the call. Forming an alliance with the Shield Hero, they face the Waves.