Hero

Hero (英雄) is a title given to the person who has made the contract with the gods or a title for a savior who saves humanity.

History
According to legends long ago, humans were ruled by the Demon King. It is said that they were treated like slaves because they could not go against the demon lord who possessed great power.The first hero stood up to break through such a situation. The first generation hero made a contract with the gods and absorbed their blood in order to gain the power to fight the demon lords and the hero who gained the power of the gods acquired dramatic power, defeated the demon king, and set the humans free.

The first hero created a child and inherited that blood. At the same time, his power was also inherited. It's been going on for generations and continues to the current generation which is now Arios inherited the blood of the first hero who was considered a chosen one. But as of now, Arios is not a full-fledged hero and is still in his growth and currently, he is not a "perfect" hero. It is because he's yet to break his Limit Break. However, Arios betrayed his ancestor's legacy to defeat the Demon Lord when he attempted to kill Rein Shroud for humiliating him in their duel but only to be easily defeated by Arios again. After his second ease defeat by Rein Shroud, Arios lost his status as a hero and sent to prison for his betrayal towards the Hero's Party and humanity as well as his reputation as a Hero was forevermore ruined, where Arios will always be remembered as a traitor. In Light Novel 8, the former hero Arios escaped from prison with a help of Monica (a subordinate of the Demon Lord) and joined the Demon Lord's army to get revenge on Rein Shroud, his companions, the former Hero's Party and humanity itself due to his ease-still-humiliating defeats by Rein twice.

After defeating the tyrannical ruler of Horizon, his son ex-mayor Edgar Fromware and the traitorous former Hero Arios, Rein Shroud (the series' protagonist) is now widely acknowledged by the citizens of Horizon as their savior by giving him a title as the "Hero of Horizon" for his heroism when he defeated those three twisted-yet-weak villains and killed one of them (Edgar who now turned into a demon).

Limit Break
This power runs exclusively through the hero's bloodline. No matter how hard humans try, they cannot acquire the power to defeat the demon king. Without growing that far, they reach their growth limit halfway through and this is applicable to even those who are talented in battle but cannot grow to the point of defeating the Demon King. At the most, the best they can do is defeat the Four Heavenly Kings because normal humans' limits are fixed.

But the hero is different. With a body that has been passed down from generation to generation by taking in the blood of the gods, there is no such thing as a growth limit for him. They can grow endlessly and accumulate power endlessly. , he'll grow to the point where he can defeat the Demon King. However, that day has never come when Arios has betrayed his ancestor's legacy just for his vengeance on Rein Shroud only for Arios to be easily defeated by Rein once more instead. Due to his betrayal, Arios lost all of his privilege as a hero leaving him unable to break his Limit Break and too weak to defeat the Demon Lord.