Right as Asmodeus was on the brink of being awakened, an obscene and devilish "Siren" has appeared. All who are seduced by this evil spirit will find themselves immersed in lust and end up getting destroyed. Meanwhile, a crusader known as "Bato" finds himself lost and struggling after losing all his comrades in a war that was influenced by evil. But as he finds himself seduced by the Siren...

(Source: Lezhin, translated)

Note: Chapter count includes a prologue.