The story starts off with a the main character Dai telling a story about how the monsters on an island he's living was possessed by a evil demon, and how a swordsman came to the land and defeated the evil demon and converted all of the monsters back into their original forms. But he immediately gets snap back into reality when his master Burasu hits him over his head. Burasu is disappointed by Rai's inability to learn a magic spell that he's trying to teach him.
Afterwords, Dai sees a ship approaching, that's filled with bandits that's planning to steal a flying golden slime; which they believe is worth a lot of gold. Dai assumes they were heroes and greets everyone. The bandits decide to fool Dai into thinking that they were heroes, just so they can have Dai lead them to the golden slime. Dai calls all of the monsters on the island and then goes and gets Gome. Burasu arrives and notices that something was wrong. The Bandits then attacks all the monsters and steal Gome away from Dai. The bandits shale away planning to sale the slime for at a high price.
Dai decides to go after the bandits and save Gome. He has the magic tube that was giving to him from Burasu, the magic tube can entrap anyone inside it. Dai then calls a Chimera out and has it fly him to the bandits' location.
The four bandits arrive to a castle where they meet the King and his followers. To the King and his followers, the four bandits are seen as heroes. Delorin, the leader of the group, shows everyone the golden metal slime. The King and the others are impressed, and reward whatever the "heroes" want, and Delorin was also given with the crown of champions; a crown that's given to those that's sought as a true hero.
The other bandit, Zurubon, goes out and shops for clothing that's sold throughout the town. She then encounter a mushroom monster in disguise, that unleashes a gas that makes everyone around it past out. The monster carries Zurubon away to a hideout where Dai and his slimes are located. Dai then interrogates Zurubon, who is all tied up, for the whereabouts of Gome, the golden metal slime. He summons out an anteater monster and has it tickling Zurubon's feet by licking them. She caves in and tells Dai where Gome is, she tells him that Gome is at the Kings garden, where a party is being held.
Dai sneaks into the castle and sees Gome unhappy in his cage. Dai then summons out all of the monsters from his magic tubes to help free Gome. Dai gets the cage that Gome is in and runs off, but is trapped by two of the bandits; Dai unleashes more monsters to save him. Dai then sees that his monsters where defeated by Delorin, and then engages into a sword fight with him. But Dai is no match for Delorin's swordsmanship, about to be killed by Delorin, Dai uses a special magic tube that's given by Burasu. The magic tube contains monsters that Dai has never seen before, but he has them attack Delorin and the other two bandits. Zurubon manages to escape and has the slimes, that are all in a net, held hostage and threatens to kill the slimes if Dai doesn't give up Gome. But Dai uses the magic tube and has the slimes combined into one giant slime that breaks out of the net and squashes Zurubon. Then Dai entraps Delorin and his magic tube.
After all that, Dai immediately pasts out from all of the action. The King then realizes that the four bandits aren't not really heroes as they resulted to tactics like attempting to Dai, a little boy that was nearly defeated, and taking someone hostage. The King sees Dai as the true hero and gives him the crown of champions. A couple days later, Dai is back on the island searching for his crown. Burasu tells Dai that he's going to be a magic users and nothing else. Dai sees that as unfair and begs Burasu for the crown. the chapter ends with Gome flying around the island with the crown on it's head.
Another ship arrives on the Delmarin Isle, Dai panics due to his assumption that the ship is a war ship that's about to attack. Burasu corrects him by saying that the ship is a Holy Ship, a ship filled with sages. Three characters introduces themselves, Temajin, the bishop of the kingdom of Papunika, a sage named Baron, and his sister Princess Leona, who is looking to become a sage. They arrive to the island due to their knowledge about Dai from the king of Romos, the king that gave Dai the crown of champions. The sages seek a place that's closes to the Earth God as part of a ritual for Leona to become a sage. Burasu tells them that place is a large cave deep within the forest. Burasu then appoints Dai to lead them to the cave.
As they were walking to the cave, they encounter a large monster which spooks everyone but Dai. Dai walks up to it and tells him to go some place else. Leona is impressed, and then ask if Dai can perform magic, but says that he's unable to. They make it to the cave and the guards prepare for the ritual. Dai is then given a dagger from Leona, thinking it suits him better. Then a mysterious person appears and summons out a demon scorpion out of a magic tube, attacking everyone including the Leona. Dai pulls out the dagger that was given to him, and slays the scorpion.
Dai sees Leona unconscious, Gome tells Dai that she is poison, and that a cure spell can save her. But Dai is not sure what to do due to the fact he can not perform a spell.
Picking up where the last chapter left off, Dai tells Gome to go get help. He then sees Baron, who reveals his true colors. Baron reveals that he was the one that released the demon scorpion so it will kill Princess Leona, and have the control of Papunika to Temajin. He then uses his magic to combusted the ground and have Dai and Leona fall into a large cavern.
Gome then warns Burasu about what has happen, just when he was about to head for Dai and Leona, he is stop by Temajin and his guards. Burasu overpowers them and summons out all of the monsters on the island to fight off Temajin and his guards. Baron arrives inside of a killer machine that he powered with his magic. Burasu and the monsters fight off Baron with all their might, but it's no use as Baron still stands.
Dai and a weaken Leona are trap inside a cavern. Dai then blames himself for not learning how to use a single magic spell, but Leona reminds Dai that he shouldn't blame himself as there's many people that don't know how to use magic. As it looks like Leona was on her last breath, the sight of Leona's condition triggers something within Dai, a big explosion occurs nears Dai and Leona's location. Dai is then seen with a marking on his forehead, implying that he must have gain a new level of strength.
Dai finally is able to perform magic spells. Manages to get himself and Leona out of the cavern, and heads for Baron. As they arrive, Dai sees Baron, about to kill Burasu, but is stop by Dai. Temajin gets upsets at Baron because of his failure to kill the Princess. Baron immediately attacks Dai with a giant arrow being shot at him, but is missed.
Dai tells Burasu that Leona is poison and he must use the cure spell to extract the poison. Baron then tries to kill Burasu before he even attempts to heal Leona. Baron shoots out another arrow at Burasu, but Dai counters it with a wind spell, which makes the arrow missed its target. Dai tries to fight off Baron's killer robot with his magic, but the strength of the killer robot still stands. Baron then gets possessed by the killer robot and betrays Temajin.
Dai uses his dagger to try to damage the machine, by Baron sees it as useless. Baron gets fooled as Dai was attacking the same spot, which he manages to crack a hole. Dai then uses a fire spell, the flames of the spell enters into the hole, inside of the robot, and Baron is attacked, then defeated.
Everything becomes good again as Leona is saved as the poison healed out of her body with the use of the cure spell from Burasu. Leona completes the ritual, and becomes a sage. The Papunika authority finds out about Temajin and Barons' scheme, and get taken into custody. Leona thanks Dai for all his help, and leaves the island. Dai attempts to use his magic again, but goes back into having trouble performing a spell.
The entire monsters of Monster Isle have been possessed, causing them to turn into murderous creatures. Dai sees what's going on, and tells Burasu about it. Burasu is also been infected, and is trying to fight it off. He's under the suspicion that the Demon King has been revived. Burasu tells Dai to leave the island before he or the other monsters attempt to do something harmful to him, but Dai refuses and wants to help Burasu, and the monsters of the island.
Then the monsters charge towards Dai with raged looks in their eyes. As that was happening, two men sail in, one of them uses his sword to make a huge marking all around the island at a extremely fast rate; it is a barrier that protects all of the monsters from the control of the Demon King. The person then introduces himself as Avan De Ginual, a hero training instructor, and his student, Pop. Avan and Pop head to the island, due to the information that was given to them about Dai's help in saving Princess Leona from the Kingdom of Papunika. Avan then tells Dai and Burasu about Burasu's theory coming true about the Demon King being revived, and having all of the monsters attacking the people all over the world.
Dai's plans becomes clear to him, that he must defeat the Demon King. But two gargoyles fly to the island and attempt to attack Dai, but is blocked off by the barrier that was created by Avan. Avan tells Pop to destroy the two gargoyles. He takes down one, but is then cast a spell over him by the other gargoyle, which makes him unable to fight. That's when Dai steps in and fights the gargoyle off with the dagger that was given to him by Leona. But the gargoyle manage to make Dai's lose his dagger and has him defenseless, but Avan tosses Dai his sword, which Avan clams it's a legendary sword. Dai unleashes a powerful swipe that splits the gargoyle in two.
Avan is in shock by what Dai was able to do as he admits that it was some random sword that he bought at a Roadside Tool Shop. Dai, Gome, Burasu, and the rest of the monsters are in celebration by Dai's victory.
Avan tells Dai that he can make him into a hero just in one week through a "Special Hard Course." Pop is against the idea as no one has never been able to complete the special hard course. Bur Dai accepts the training, knowing that he must save Princess Leona and the rest of the world from the Demon King's terror.
The special hard course consist of Dai running along the island with boulders tied to his waist, freezing a ocean wave, and mediating while being upside-down. For his first day, Avan carries in a giant boulder that Avan wants Dai to cut. Dai uses the "legendary sword," but the sword breaks once it makes contact. Dai then uses his other weapon, the dagger, but fails to do any damage, so Avan decide to save that part of the training some other time.
As the end of the first day approaches, Avan ask Dai to cut the giant boulder again, but Dai is too weak from his training and feels he can not do it. Avan says to him to "trick his mind" into thinking that he can do it. Dai then takes a swipe at the boulder, and surprisingly damages it. Avan explains that when he is tried and confuse, Dai limited himself into one action, which made him able to cut the boulder.
The next day, Avan is amazed to see Dai's swordsmanship has improved, giving Avan a serious challenge. Avan then shows Dai his finishing technique that he wants Dai to learn at the end of the second day, "Avan Slash." Pop, who is behind a bush watching the training going on, is spotted by Avan and tells him that he's welcome to participate in the training.