Maou Gakuen no Hangyakusha is a Manga/Manhwa/Manhua in english language, Ecci series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

Yuuto is an ordinary high school boy who, one day, notices a mysterious tarot card by his bed. He shows it to his parents, who give him the good news - as the son of demonkin, he is eligible to become the next Demon Lord. As such, Yuuto is soon brought to a demonic academy in order to improve his devilish skills and earn the title of demon lord. And, you know, get a harem along the w