The supreme ruler of Hell and the ultimate superior of the protagonist, Go Sun-ho. His core characteristics are as follows. Unexpected Generosity: To Go Sun-ho, who directly questions the absolute rules and laws of the Underworld, he coolly grants permission to establish the Underworld Insurance agency, saying, "Go ahead and do whatever you want." He has a magnanimous side, watching his subordinate's bold challenges with interest. Merciful Consideration: When fellow Grim Reaper Lee Seok-ha was first appointed, Yama personally arranged for a specific memory from his human life to remain. A Terrifying Absolute when Angry: Usually like a flexible and generous department head, his essence is the King of Hell. The reason Lee Seok-ha gets scared and warns Go Sun-ho, "Do you want to become a bug?!" whenever he acts out is because of King Yama's wrath. Firm Judgment: In the 'Comrades' arc, he showed great rage toward situations that crossed the line. He is a figure who leaves a clear impression of absolute dignity and terror, such as giving a final chance to Lee Seok-ha's former police colleague by sending him back to the living world.

A Principled Grim Reaper: He has the opposite personality of Go Sun-ho, who opened an insurance agency out of doubt for the irrational laws of the Underworld. He is an 'FM' (Field Manual) civil servant type who follows the laws of the Underworld exactly and remains faithful only to his assigned duties. Signature Appearance: He wears the traditional black gat (hat) of a Grim Reaper and carries a large scythe. Go Sun-ho's Dedicated Cleanup Crew: When the protagonist Go Sun-ho refuses to guide a soul or tries to use tricks to give them benefits because he's moved to tears by their story, Seok-ha coolly cleans up the mess behind him and guides them instead. King Yama's Brake: Whenever Go Sun-ho acts recklessly, he gets flustered and shouts childish yet realistic lines like "Do you want to become a bug?!" to warn him of King Yama's anger. 2. Hidden Past and Narrative (Memories of the Living World) Former Police Officer: Before becoming a Grim Reaper, Lee Seok-ha's original profession in the living world was a police officer. King Yama's Consideration: While the rule is to erase all memories of the living world upon becoming a Grim Reaper, he started his duties with one specific memory intact thanks to King Yama's special permission. Bond with Comrades: According to the 'Comrades' episode, there is a touching anecdote where King Yama, despite his great anger, considered Lee Seok-ha's circumstances and gave a former police colleague a final chance by sending them back to the living world when they were in danger.