Dainana Maouji Jilbagias no Maou Keikokuki

Alexander, whose hometown was destroyed by the demon race, fought with the Demon King and was killed. But, although he should have died, he was reborn as the Demon King’s son, Jilbagias—!? While hiding his true identity, he stains his hands with atrocities as he conducts himself as the ideal demon prince, increasing his power to ultimately overthrow the Demon Kingdom... (Source: Mangamonster.net)