Dainana Maouji Jilbagias no Maou Keikokuki  

Dai Nana Maouji Jilbagias no Maou Keikoku-ki, 7th Demon Prince Jilbagias, The Demon Kingdom Destroyer

Alexander, a warrior from a town that was destroyed by demons, confronted the Demon King and met his end. However, instead of going to the afterlife, he woke up reborn as Jilbagias, the son of the Demon King. To conceal his true identity, he committed horrific acts while pretending to be an ideal demon prince. Through this deception, he amassed immense power and eventually led a rebellion against the Demon Kingdom.