Magan no Fukushuu-sha - Blood Parasite

"Would you like to be part of my family?" Archive, the devil race's weakest, was saved by the Demon Queen right before death overtook him. Unable to have children and capable of harming anything that approaches him, Archive is the only member of the Demon Queen's "family" that continues living. However, demons and humans hate each other, and they are fighting wars at the cost of each other's peace. Eight heroes lure the Demon Queen with promises of peace to defeat her. Archive could only stand by and watch as the weakened Demon Queen fell into the trap and then abused. Archive goes to help, but as the weakest demon, he has no way to fight back and meets his end as his head was severed from his body. The Demon Queen is then sealed away. Unable to protect the Demon Queen, Archive used every ounce of his strength to cast a certain spell on one of the eight heroes, Lieselotte. [Forbidden magic that kills and takes over the soul of a fetus called Blood Parasite]. By using this magic, Archive managed to take over Lieselotte's fetus, as she was already pregnant. Reborn from the weakest demon into the son of a hero, Archive would eventually display "Demon eyes." Petrification, Charm, Fear, Clairvoyance, along with other powers that became available to Archive, who had obtained the most powerful demon eyes. Archive vows revenge on the heroes, even if it was his own mother who gave birth to him, or the lover who loved him when he was a teenager. “Just you wait, heroes, I shall kill you and take back the Demon Queen!”

Official Translations:
T.Chinese