Idle Devils

The Demon World was infected with a violent miasma, which caused chaos in the Demon World. The Demon King sealed the infected people in each hell with the staff of stars. 200 years later, the seal of the Demon World was broken, but this time the Demon King failed to seal it, even swallowed himself, and the Demon World fell into chaos again The new king of the Demon World is selected. The one who can seal the seven hells again is the new king.