"Listen up, my beloved descendants. Your founding ancestor has returned." The most powerful Demon King in history, Anos, known for his tyrannical rule 2000 years ago, has been reincarnated. Entrance exams are being held at the Demon King Academy where they train his descendants to be his successor and become Demon Lords. The entrance exam is a practical test where students must duel each other. Bored of the war-torn world of 2000 years ago, the tyrannical Demon King, Anos, appears on the scene.

Though he is the founding ancestor and possesses enormous magical powers, Anos is cast as a misfit at the Academy. Unperturbed by this unjust treatment, he continues to demonstrate his overwhelming powers and takes part in the team competition exam as a leader. His classmates mock him for being a hybrid, and the only teammate he can find is Misha. Their rival team is led by Sasha, Misha’s older sister, who looks down on Misha and calls her a "junk doll."

"One last thing, I’m glad I got to meet you." Without being able to understand Sasha’s true intent behind these final words, much time has passed, and Ivis, one of the Seven Elder Demon Emperors, holds a special class at the Demon King Academy called the Great Magic Training. The Seven Elder Demon Emperors are seven demons that Anos, the founding ancestor, created from his own blood. Emilia implores Anos to act respectfully to Ivis, but without hesitation, he speaks to Ivis in a condescending tone.

Misha confesses the shocking truth that, "At midnight on my 15th birthday, I’m going to disappear." Misha was never supposed to exist in this world in the first place, but due to Ivis Necron’s magic, she was living a transient life. She had resigned to her fate that she will only live for 15 years, but Anos tells her, "There are two things that I do not understand. Regret and saying that something is impossible." The misfit crushes the tragedy and unjust fate that binds the two sisters.

Shortly after Anos’ encounter with Misha and Sasha as well as his battle with Ivis, a transfer student named Ray enters the Demon Academy. As the Master of Magic Sword and powerful enough to defeat the Seven Elder Demon Emperors, Ray makes it clear that he wants to join a team with a capable leader, and requests to join Anos’ team. However, Anos refuses and proposes to Ray that, "If you prove that you are worthy, I will allow you to become one of my followers." Ray decides to form his own team and battles head-to-head with Team Anos during the team competition exam.

In recognition of their accomplishments in the team competition exam, Anos welcomes Lay and Misa to his team. The team gathers at Anos’ home to celebrate, but shortly after, Lay and Anos are announced as participants in the Magic Sword Tournament. Lay rejoices at the chance for a rematch with Anos, but Anos suspects that there is an ulterior motive. The situation escalates when Misa takes Anos to meet one of the Seven Elder Demon Emperors, Melheis Boran.

Anos resolves to defeat the Royalists no matter what tricks they have up their sleeve. He uses the sword received from his father Gusta to fight in his first match in the Magic Sword Tournament. Meanwhile in the dressing room, Lay clutches his chest. Sensing that something is wrong with Lay, Anos speculates that somebody is controlling Lay and a hostage may be involved. Who is conspiring to control the Magic Sword Tournament from behind the scenes?

Anos and Lay battle head-to-head at the Dilhade Magic Sword Tournament finals. With Sheila being taken hostage, the two are unable to fight at their full potential and come to a decision. Just as the showdown reaches its climax, a huge Magic Circle appears in the arena. The scenery around Anos and Lay begins to distort, and they are taken into an alternate dimension. The mastermind behind the recent events finally reveals his true identity.

After the Magic Sword Tournament, Anos and the other students visit Azeshion in the Human Realm for an educational exchange with the Hero Academy. While they individually explore the city, Anos heads to the Hero Academy saying that he wants to research something. The academy is off-limits to outsiders, but without hesitation, he tries to make his way inside. Eleanor Bianca, a third-year student at the Hero Academy, appears before Anos and says, "You’ll be safe as long as you’re with me" with a mischievous smile. She acts as Anos’ guide inside the academy.

Anos and the students from the Demon King Academy participate in their first day of inter-academy exchange with the Hero Academy. However, the students from the Demon King Academy soon find out that the inter-academy exchange is in name only, and they are met with outright hostility. Revest, a third-year student at the top of his class from the Demon King Academy is ridiculed by the students from the Hero Academy when he unsuccessfully tries to activate a magic spell. The students from the Demon King Academy are visibly offended by this treatment, but Anos’ words turn the tables. "As usual, humans sure like to set traps for us, don’t they?" The inter-academy exchange is off to an ominous start.

Round 2 of the inter-academy exams begins. After Revest’s deplorable defeat against Heine, Anos and his team battle with the students of the Hero Academy. Anos says that he will think of a strategy if it becomes necessary, and clashes head-on with his enemies using his vast Magic Powers. However, due to a magic barrier called De Igelia that is cast over the entire city, and a young girl named Zeshia who wields the holy sword Enhale, Anos’ attacks prove to be futile. Anos and his team are unable to come up with their next strategy, but Misha proposes a plan that could help them win.

"Please, the only person who can stop Zeshia is me." Anos carries Misha, who is on the brink of death after being attacked by Diego, to an inner room of the temple. Eleonore is waiting there and claims that she is "the embodiment of magic itself." She explains the meaning behind this and exposes the madness that has taken ahold of the Hero Academy.

Everything started two thousand years ago. The situation suddenly shifts when the true identity of the man in the black mask, Avos Dilhevia, is revealed. Even after two thousand years, the wounds caused by the endless conflict between demons and humans have not been healed. The Demon King of Tyranny, Anos Voldigoad, makes a choice…