It’s already been 18 years since the last Great War between the Demon King and the entire world. Since then, the Demon King’s throne has remained vacant.
 
Hayato Nakamura, a half-human and once-in-a-millennium magic genius, studies at the prestigious Sylvania Magic Academy for heroes, trained to fight against demons.
 
However, due to a series of fortunate—or perhaps unfortunate—events, he suddenly inherits the title of Demon King.
 
But demons are inherently vicious, bloodthirsty creatures who believe in the survival of the fittest, obeying only the strongest.
 
As a young and new student at a school meant to nurture the next generation of heroes to fight against the Demon King, he is far from being the strongest. His adventure is only beginning. 
 
Now, caught in the deadly web of demon world politics, Hayato must navigate his new role while trying to survive. He also has to watch out for trouble within the academy, especially from the prophesied Hero. 
 
To make matters worse, Hayato has an incurable disease that prevents him from using magic, his greatest strength.
 
Now, he must embark on a journey to find a cure while simultaneously claiming his rightful throne.
 
But how can he survive without his magic, especially when the entire world is against him?

A/N: Hayato is an apathetic antihero, a Demon King. He does not hesitate to kill, but he is not a psychopath who goes on a killing spree for fun. The academy is not the main theme; it is only a minor part of the story. The novel mainly follows Hayato—his adventures, dungeon exploration, the demonic continent and its politics, and romance. This is primarily a weak-to-strong progression story, so understand that the MC is not overpowered from the start, though he will still possess conditional strength from the early stages. 

I am a slow writer.

1. The prefix 'Pan–' comes from Greek, meaning 'all' or 'including everything.' So 'Pan-Human Alliance' means 'an alliance that includes all of humanity.' 


2. Sumiko means longevity and beauty in Japanese. Aonami means blue wave.


3. In a historical context danna-sama meant master. In modern usage danna-sama is a very respectful way to say husband. 


4. El Salvatore, the artificial island, was created approximately 700 years ago by the Sage Sylvania. Around 500 years ago, the renowned Sylvania Magic Academy was established on the island. 


5. Mana's Bane is an artifact created over 400 years ago. Its creator remains a mystery to this day. 


6. Sil is the name of the currency of this world. 


i. 100 Copper Sil = 1 Bronze Sil = 1 Dollar


7. Hayato's Likes: Mango lassi, cold coffee, family... 


Hayato's Dislikes: Chocolates, hot coffee, idiots... 


8. The Demonic Continent is called Hellhelm. Its capital is Pandemonium, the city where Demon King Asmodeus resided. The capital of the Beelzebub clan's territory is Findias.


9. Mana's Bane (Rare): A red pendant that grants a low- to mid-rank familiar contract. Only one contract can be established. The contract cannot be dissolved unless either the familiar or the contractee dies. If the contract is broken, the familiar dies. It is a bound item that Hayato owns. Kursh is contracted through this. 


10. Magic Ring (Rare): An item box that stops time for anything stored inside. However, it cannot withstand excessive mana, so only mid-rank items can be stored within it. It has a storage space of 12 × 12 feet. Hayato owns this. 


11. Del Heim's Glasses (Rare): Glasses that inhibit recognition. They can also be used for disguise, allowing the user to freely choose who is unaffected by the recognition-inhibiting magic. They can also grant invisibility. Hayato normally wears this glass. 


12. Eons ago a certain demon had spread the present common language as the Universal Language. 


Trivia.