Third part of Douluo Dalu.

Kyou kara Maou! revolves around Yuri Shibuya, your average Japanese teenager. One day, Yuri sees a classmate being harassed by bullies. Thanks to this intervention, his friend is able to escape, but unfortunately Yuri becomes the new target of the bullies in the process and gets his head shoved into a toilet. But instead of water, the toilet contains a swirling portal that sucks him into another world, largely resembling medieval Europe. There, he is told that he will become the next Demon King due to his black hair and black eyes, traits only possessed by the demon's royal lineage. Yuri's arrival is met with some skepticism by some of the demons, who view him as unworthy to be their king. However, after Yuri wins a duel by utilizing his magical powers, the demons slowly begin to acknowledge him as their monarch. Yuri must now learn what it takes be a true Demon King, as he tries to keep the peace between demons and humans in this strange new realm.

As she heads off to her entrance ceremony at Sainotama Girls' High School, Akane Kikuchi muses over her grade school dream of becoming a manga artist and the lack of progress that she has made. When she finally arrives at school, she is surprised to learn that she is once again in the same class as her two best friends: the deadpan and emotionless Shiori Saginomiya and the hyperactive and ridiculous Nozomu Tanaka. Tanaka then comes to the obvious realization that she can't achieve her grade school dream of being popular with the boys and getting a boyfriend by going to an all-girls high school. In desperation, she begins asking the girls in her class to introduce her to their guy friends. Her classmates, however, are anything but ordinary. From a grandmother-loving loli to a reclusive chuunibyou to an overly analytical stalker, each one is given a fitting nickname by Tanaka to accentuate their weirdness. And so begin the wasteful days of these high school girls, each day kicked off with a simple question: "Hey, wanna hear something amazing?" [Written by MAL Rewrite]

The world is divided into two kingdoms: the Kingdom of White, which floats in the heavens and is ruled by their queen Iris, and the Kingdom of Black, which stands upon desolate land below and houses the King of Darkness as its ruler. As of late, forces of evil have amassed great power, posing a threat to the entire world. Being the main representative of the Light, it is Iris' duty to maintain the balance of the world and fight off the darkness in her kingdom. Meanwhile in the Kingdom of Black, rampaging monsters annihilate a certain boy's village, leaving him the sole survivor. As he grieves in hopelessness, an armored man named Skeer notices the child and comforts him. Soon after, Skeer recognizes the boy's potential to change the kingdom's status quo and makes him his heir before passing away. The boy then vows to become the Prince of Darkness—the one who will replace the King—to bring the world back to its rightful path. As Iris and Prince of Darkness each challenge the impending doom the world faces in their own respective ways, their destinies will converge with each other, and perhaps, their bond will decide the fate of the world. [Written by MAL Rewrite]