Ard Meteor sits at the dining table on the evening of his tenth birthday and enjoys his meal while his parents celebrate around him. To everyone in the village of Brave Nest he is an ordinary boy, the son of a completely average couple. That is what they all believe.
In reality he is the reincarnation of Varvatos, the most powerful demon lord in history. He spent his previous life feared by the entire world, and in all those years of being feared he was never able to make a single true friend. He grew so bored of it that he chose to be reborn thousands of years later. That demon lord was fed up with winning again and again, because every challenger capable of defeating him was gone. To be seen as an equal by ordinary people, he decided to reincarnate so that he could live as a normal human. His wish came true soon enough, and he was born again as Ard Meteor, the son of a completely average couple.
While he eats, he thinks about the books from his own time, and he realizes that both magic and education in this world have declined quite a bit since his days as the demon lord. Besides being intelligent, he is also blessed with great physical strength and stamina. His parents ask him about his plans and his dreams, and the question makes him pause for a moment, because he still hasn't decided.
After finishing his meal, he realizes that he needs to make more friends and earn the trust of the villagers. He has already matured far beyond the others around him, because his mind is the mind of a grown man. He looks out of the window and spots three boys playing on the road, and he waits, hoping that they will come over and become friends with him. Instead the boys notice him, decide that he looks creepy, and run away, leaving Ard confused. He decides it would be better to approach people himself than to wait for someone to approach him.
He steps outside and notices three girls walking down the street. The moment he sees them his stomach starts hurting from anxiety, and the pain forces him to sit down on the ground. The girls notice him, get creeped out and immediately try to run. Ard quickly stops them and gathers the courage to ask whether they would be his friends. Instead of answering, they become even more frightened and start running away even faster, leaving Ard completely heartbroken.
Later that day Ard grows frustrated and begins destroying trees while practicing his magic. He stops himself before he can start damaging the ecosystem and heads back home, wondering how on earth he is supposed to make a friend.
Just then a man named Olhide approaches him and learns about Ard's struggle. Olhide suggests that he simply be kind and respectful to others, explaining that it will help him make a great many friends. Hearing that, Ard becomes excited and quickly runs off toward the town, hoping to test the advice and gather plenty of friends at last. Ard's parents watch him go, and admit that their son sometimes behaves strangely, to which Olhide awkwardly agrees.
Inside the town Ard stays completely kind and completely respectful as he asks a group of boys, and then a group of girls, to be his friends. Both times he is indirectly rejected.
Frustrated, he heads back out of the town, and when monsters try to attack him in the forest he kills them angrily. After he has calmed down, he realizes that anger only brings destruction and chaos. At that moment he hears a girl screaming somewhere in the forest, and he is curious enough to use his magic to fly toward the sound.
There he spots a girl fighting an ancient wolf, which is in fact a very weak monster compared to the other creatures living in the forest. The girl uses her magic techniques to overpower the wolf and eventually defeats it. Once the fight is over, Ard watches her closely and recognizes her: she has the face of Lydia, a girl he knew in his past life.
He approaches her and tries to compliment her on her skills. Lydia's face frightens him a little in return, and he politely asks her to be his friend. Since she does not immediately panic, Ard thinks that this might be his chance. He walks closer, believing that the two of them are about to become great friends. Instead the girl starts crying and runs away, pointing out that he doesn't know anything about her and still wants to be friends.
Ard becomes confused and returns home, only to find her there, hugging her father, Sir Olhide. That is where he learns that her real name is Ireina. Excited by the discovery, he tries harder than ever to become Ireina's friend. She only gets more creeped out and keeps avoiding him. Even after being rejected many times, Ard refuses to give up and keeps trying.
One night Ard looks back at every strategy he has tried and realizes that not one of them has worked. He lies on his bed, thinking up new ways to make friends, and is startled by the sudden screams of the villagers outside. He steps out of the house and spots monsters attacking the village. Before he can use his magic, his father arrives and starts fighting the monsters himself.
Olhide rushes over and tells them that Ireina is trapped among the monsters out in the forest. Hearing that, Ard immediately takes off toward the forest, assuring Olhide that he has nothing to worry about.
Surrounded by monsters, Ireina is completely terrified as she stands there alone. She thinks back to all the times when people called her a monster, and to how she could never make a single friend, and it leaves her feeling even more hopeless. She drops her weapon and tells the monsters to do whatever they want with her. As the goblins charge toward her she is frozen in fear.
Ard arrives just in time and uses his magic barrier to protect Ireina from the goblins. As she watches in surprise, he lands on the ground and uses his magic to wipe out almost all of them. The monsters' leader is left stunned by the boy's incredible power. He quickly orders the remaining two goblins to charge at Ard, but Ard uses his magic to blow them apart before they can even reach him. Terrified, the leader tries to escape. Ard does not let him get away, and uses the same technique to blow the leader's head apart as well.
Meanwhile, back in the village, Ard's father Jack manages to defeat all of the monsters. Then they wait for Ard and Ireina, confident that Ard will save her and bring her back safely.
Just as they expect, Ard saves Ireina from the monsters. As he approaches her, she breaks down in tears and admits that she is completely alone. Ard gently assures her that he wants to be her friend, but she compares him to her old friends and says that he will leave her too. Ard reassures her that she has nothing to worry about, and promises that he will never leave her. He goes on explaining that Ireina deserves to have friends, and that he truly wants to be one of them.
The two of them finally become friends, and they continue to grow stronger together for several years.