Demon King Daimao (2010)

S01E01 The Demon Lord Is Born!

On the train to Constant Academy, Akuto Sai encounters Junko Hattori, and together they swear a solemn pact to improve the world—one that carries a death penalty if violated. Once he arrives, the school labels him a future Demon Lord, and fear spreads among the students. His passionate class introduction earns admiration from Hiroshi Miwa but deepens everyone else's terror. Later, Akuto mistakenly volunteers for "cleaning duty," Constant's code for becoming a "cleaner," an assassin guarding the school's secrets. Enraged, Junko challenges him; their duel ends when Akuto accidentally blows up the classroom. His attempt to apologize at her dorm only provokes another deadly rampage, leading to a forest chase. There he meets Keena Soga, who vows to shield him for private reasons but fails, and the fight concludes with yet another explosive mishap. Right after, Korone, an "observer," appears before him.