The manga centers on the titular Clevatess, the lord of all magical beasts, who wields both uncanny intellect and destructive power. Bothered by the 13 heroes tasked to destroy him, he has decided to be rid of humanity once and for all. However, he has been charged with one nuisance: the care of a newborn human baby. Now the world stands upon the brink of Armageddon, with the obligation of raising one child holding it all back.