How NOT to Summon a Demon Lord Vol. 6 (manga)

DEMON LORD VS. DEMON LORD

All her life, Rem has carried the soul of the demon lord Krebskulm inside of her, terrified of letting such an evil loose on the world. But now a mysterious Fallen has told Diablo, Rem, and Shera about a ritual that could free Rem. The catch is that it means letting Krebskulm free as well... Can Diablo, a fake demon lord from the ordinary world, take on the real deal?!