One day, Ryusei Homura and all his classmates are transported to another world where they are asked to help in defeating the 12 Demon Kings. Ryusei was always looked at as an idiot, a weirdo and a pervert who always stares at girls’ breasts. He was always bullied and beaten up after school. Even after the summoning, he ends up being the weakest in his class. And eventually, in the midst of a battle: "We don't need to look after trash like you. You're just a burden, so die!" Ryusei was killed by one of his classmates. As everything turns dark for him, the Demon God offers him a deal: "I can give you a second chance. I will make you a Demon King. I will give you power. You will be able to get revenge and live your life as you please!" But there was one thing the Demon God didn't mention to Ryusei, and when he woke up: "WHAT!? Why the hell am I a loli!?" Now Ryusei must live as the Demon King of Insanity, Milla Walpurgis.