After a decisive battle for humanity's survival, Max and his companions triumph over the fearsome Demon Lord. In his final moments, the vanquished Maou swears to return even stronger for vengeance. A decade later, Maou is resurrected but in a child's form due to an incomplete process. Eager to settle the score, Maou visits his old foe, only to find the once-heroic Max now a mere shadow of his former self. Despite this, Maou decides to stay with Max, intent on restoring him to his former glory. As Maou delves deeper into the past decade, he uncovers a mysterious tale behind Max's decline that had eluded his knowledge.