A long, long time ago, 500 years from now, there was a very wicked Demon Lord named Elleusha, feared by all living things.

Guest and Elleusha were rivals who fought every single day without fail. Though they hated each other, they naturally forgot one another as time passed, and after a long period, both were reincarnated into new lives.

Then one day in 2026, Guest was living happily, cohabitating with his beloved girlfriend, Kim Nayeon.

While peacefully watching TV with his girlfriend as usual, a light suddenly flashes in the middle of the living room...