"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.

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…

Erdomaid DittiJohn, one of the four evil royals, has appeared before Anos as a teacher at Demon King Academy. Not only that, he claims himself to be the Heavenly Father God NousGalia, and that the new "Child of God" who will vanquish the Demon King of Tyranny is also at the Demon King Academy. The “Misfit” who overcomes all odds sets off to a new battle!

In order to visit the Spirit King, Anos and his team continue to go through trials provided by the Great Tree Spirit Enyunien. The next trial, “The staircase of Geunier” is a trial where they must choose the 5 correct paths out of the 20 paths before them, which appears to be a game entirely dependent on luck. However, thanks to the advice from Lena, Anos and the team individually made their ways to the top. Lay and Misa arrive to the Spirit King’s castle first, and engage in the final trial!

Anos and the others continue their investigation in Aharthern. Although he wasn’t able to switch his source as Avos Dilhevia as the Demon King of Tyranny, Anos receives an important hint from Leno. Lay engages in practicing swordsmanship with Shin. After this, Anos follows after Erdomaid to Delsgade. There, they encounter Demons who were ruling over humans.

Avos Dilhevia takes control over Magic Sword of Destruction Venuzdnor at last. Anos gives a calm smile to the enemy who seizes everything from the Demon King of Tyranny and reigns control, however... The true purpose of Avos taking control over the Magic Sword at the end of the fierce battle is revealed. How does Anos face off against the Child of God, destroyer of the Demon King of Tyranny, and the power that destroys all life!?

The Mythical Age. In an effort to destroy the Moon of Creation, Anos meets the Goddess of Creation Militia and begins to interact with her. And now the present... Anos, who has made his identity as the Demon King of Tyranny known throughout the world, joins classes at Demon King Academy as the transfer student, Anoshu. To train even stronger demons, Erdomaid instates the Great Demon King Drills. As the first initiative, swordsmanship training under Shin begins!

A horde of dragons approaches Azeshion! To protect their homeland with their own hands, the Hero Academy students set out to slay the dragons without the help of Anos and his friends. Under Emilia’s command, the Hero Academy students engage in a battle to the death. Meanwhile, Lay and Misa wind up in a predicament after being captured by Lysius…. Anos and the others head to the Underground World to take care of their own agenda. There, he learns that Ahide is controlling the Draconids.

Arriving in Giorhaze, capital of the Underground World Giordal, Anos follows a wary Erdomaid to a church. There, they obtain a Pledge Jewel which summons dragons. Furthermore, Erdomaid sees Naya’s aptitude and makes a pack with her after learning her plan. Anos hears about Ahide’s actions from the bishop of the church and decides to catch him before he meets the pope.

The battle between Dilhade and Giordal intensifies! However, Anos becomes suspicious of Giordal's small fighting force. After seeing Cannibal flying out of the castle and noticing he has eaten the song of a Divine Dragon, Anos comes to one final conclusion. The 1,500 years of prayer that Giordal had continued for so long…was a never-ending barrier separating the two irreconcilable nations.