Mame no Fukushuusha: Blood Parasite

"Would you like to be part of my family?" These words from the Demon Queen offered a lifeline to Archive, the devil race's weakest member, rescuing him from the brink of death. Archive, unable to bear children and cursed with a harmful touch, becomes the sole survivor in the Demon Queen's "family." In a world where demons and humans are embroiled in war, the Demon Queen is lured into a trap by eight heroes under the guise of peace talks. Archive, powerless and deemed the weakest demon, can only watch as the Demon Queen is captured and tormented. Archive attempts to intervene but meets a tragic end, beheaded in the struggle. With the Demon Queen sealed away, Archive, in his dying moments, channels his last strength into casting a forbidden spell, Blood Parasite, on Lieselotte, one of the eight heroes who is secretly pregnant. Archive's spirit is reborn through this magic, taking over Lieselotte's unborn child. From the weakest demon, he is reborn as the son of a hero, later manifesting "Demon Eyes" with abilities like Petrification, Charm, Fear, and Clairvoyance. Fueled by vengeance, Archive vows to destroy the heroes responsible for the Demon Queen's downfall, even if it means confronting his own mother. "Just you wait, heroes, I shall kill you all and bring back the Demon Queen!" he declares, setting a dark path ahead. Note: Chapter count includes a prologue.