In the pure home of the Shishigami clan, Kuro and Keita prepare to face Reishin Shishigami and stop him before his terrible vision for the future is realized. Despite what Kuro and Keita know about the shared history of humans and the mototsumitama and the events that led to mototsumitama dominance, Reishin's plot to downsize the human population is too cruel to bear! But in the heart of the Shishigami's territory, an unexpected enemy arises to decisively correct the imbalance of the world - the ancient genuine ones themselves! With such mighty foes before them, do Keita and Kuro have the strength to change the fate of all mankind?!