Maou Gakuen no Hangyakusha

Story:

People are nothing more than the slaves of demons. Yuuto Morioka, an ordinary high school student who was chosen as a candidate for the next Demon King. But he was awarded devil's school students However, meeting a beautiful demon girl, Himegami Rizel, changes Yuuto's life and world. "I will make you the next Demon King." This is a special power that demons do not have, and it is only available to you, Yuuto. The person who is a candidate for the post of Demon King, Defeat the strongest demons as far as possible to become the Demon King, climbing to the top of the demon!