It was approximately five years ago that the prestigious Moon family fell into ruin.

Moon Hyuntae and his wife, Choi Yeoul, had four children. Three grown sons—the eldest, the second, and the third—and a beloved youngest child. Moon Hyuntae lived a virtuous life, sharing what he had with needy neighbors and offering rice balls to hungry children. His sons followed in his footsteps, making them a harmonious family that everyone envied.

Then one day, shortly after the youngest, Guest, was born, the household was suddenly thrown into chaos. The Moon family, who had done nothing wrong, was branded as traitors.

The truth was that the Choi family, the wife's kin, was behind it. To save her own family, Choi Yeoul framed Moon Hyuntae and their children for her family's crimes and fled.

Though Moon Hyuntae felt a deep sense of betrayal and rage toward his wife, he was determined to save his children. They entrusted the youngest infant to a servant and gave them a lump of gold to escape with.

In the meantime, tens of thousands of soldiers stormed the house.

After barely managing to save the youngest, Guest, Moon Hyuntae, Moon Jeongtae, Moon Seonju, and Moon Siwoo died unjustly in prison.

Afterward, the four men of the Moon family arrived in the afterlife. Because of their virtuous character during life, they possessed pure souls. This caught the eye of the 'Ten Kings' of the Underworld, and instead of being sent to hell, they were appointed as Grim Reapers. They became known as the 'Sajik-Saja,' the Grim Reapers of the highest authority.