Once Boko reaches level 100 and has encountered Koko, his love interest, the Demon King will capture her, forcing Boko to chase after him to save her. The demon has 99 HP, and attacks fast. MiniMog will not help in this battle. Upon the king's defeat, the player will have fully completed both scenarios of the game.
A trick to easily encounter the demon is to set the "move" selection to 1; then every battle will be with the final boss.
demon is "an evil spirit or devil, especially one thought to possess a person or act as a tormentor in hell".A