The story takes place in the Evil Academy where Lord Mao, the Academy's Top Honor Student (because he has never been to class), has decided that he needs to gain "the Power of the Hero" to get revenge on the Overlord, who also happens to be his father, from thousands of hours of research into comics, anime and video games. Along the way he meets Raspberyl who introduces herself as an old friend of Mao and the Academy's Number 1 Delinquent (as she does all her homework, has perfect attendance and volunteers in her spare time). Soon after, the pair meets Almaz who has come to protect the Princess from the Overlord. Mao, seeing Almaz's title as "Hero", kidnaps him while Beryl tries to rescue him. Eventually Mao gets away with Almaz as class starts and Beryl cannot be late. Mao then takes Almaz into his heart where they can switch titles thus giving Mao the power he needs to defeat the Overlord (he then comments how economical the game is as the final boss will be defeated in the first chapter). Mao and his slaves, including Almaz who is now a "Demon-in-training", then go face the Overlord who is much bigger than they expect. The fight actually occurs without the Overlord's knowledge on the palm of his own hand and the party is thus defeated.
Chapter 2 opens with Mao determining that Almaz is a fake hero and that is why the title did not grant him the power needed to beat the Overlord as he saw in his comics. As a result, he plans to shed the fake hero title as he fears it has tainted his reputation. However, upon returning to his heart he finds it locked up and he is unable to get the title out. He later finds out that to restore his proper demon title he will have to try to open his heart, something no demon, not even Beryl, has done. Meanwhile, Almaz slowly becomes more scheming attempting to manipulate Mao to do good. On several occasions, Mao catches on and praises Almaz for his underhandedness. Geoffrey then gives Almaz a time limit of 666 hours until he becomes a full demon which serves as a count down (similar to the "Hours left to finish the mission" in Prinny: Can I Really be the Hero?"). We also learn that the reason Mao wants revenge on his father so bad was because his father accidentally stepped on and destroyed a video game console enraging Mao over its loss. The Overlord offers to buy him a new one, but Mao will not be consoled as he will have lost over one million hours of gameplay data including a lot of boring level grinding.
Chapter 2 continues with Mao looking to find a dragon's egg somewhere in the old abandoned part of the Evil Academy. After Geoffery locates an egg and teleports the group to the spot, Almaz is surprised to find they don't have to "grind a few levels first" because "that's always how it is". It isn't long until Mao, Almaz, Beryl and her friends find a dragon egg only to be attacked by the elusive culinary arts students who specialize in a class so secret that few students even know the location of the classroom. Mao and crew fight off the students and claim the egg only to find that they have no way of cracking it. Beryl then determines the only way to open it is with the help of Champloo the Academy's Home Ec. teacher. However, Champloo doubts their ability to master Home Ec. and fights them for the egg, but Mao wins and successfully cracks and eats the egg with hot sauce (claiming that people who eat eggs with salt and pepper should be put to death). Upon returning to Mao's heart, however, they find that it still isn't open. The group defeats some "Saucy Maos" (yellow palette-swapped versions of Mao) in Mao's heart. After the battle, Mao regrets eating the egg with hot sauce, followed by Almaz speculating that defeating the Saucy Maos changed Mao's preference for hot sauce on eggs.
Chapter 3 opens with Mao lamenting his inability to open his heart. However, Mao's depression is short lived as he soon learns that student elections for Freshman Class Leader are upon them. Since no one has ever been overlord without becoming Freshman Class Leader first, Geoffrey guides Mao along the path to become the Class Leader. However, Mao learns that Beryl has been kidnapped by the Evil School Board for brainwashing. Mao decides that he wants to go save her and when Almaz points out that would be heroic of him, he quickly rationalizes that a brain washed Beryl would be competition for the Number 1 Honor Student title and that resisting authority by destroying the school board is the ultimate act of defiance an honor student can take. Much to Geoffrey's dismay, Mao drops out of the running and takes on the school board eventually rescuing Beryl with the help of Champloo. Upon his return to the academy, however, Lord Mao finds that despite dropping from the race, the Freshman class thinks so highly of him that they have elected him Class Leader anyway. Mao stands, at first stunned, but later triumphantly before the crowd that is now chanting his name. Geoffrey becomes even more irate at this as he believes that demons should be feared leaders, not loved leaders.
Chapter 4 begins with Mao noting Almaz has a crush on the princess of his kingdom. He believes that love is the source of hero's power and can use it to defeat his dad. Deciding to attend a Captivation Class, the news spreads throughout Evil Academy which has the Vato Bros. trying to stop Mao from going to class. Along the way, they see a new transfer student on her first day which happens to be Princess Sapphire, from Almaz's kingdom. She ends up killing Warslugs on her first day, noting that it is a bad habit but she is soon surrounded. Mao and Almaz intervenes, afterwards, they learn of Sapphire's true intention of defeating the Overlord and is attending the same Captivation Class. She decides to follow them to class and Mao notes he'll learn how to harness love energy with her in the party. In class, Sapphire meets Raspberyl and notes how cute she is before hugging her. As the group is watching a captivation video, Mao believes he finally has love energy and goes into his heart to remove Almaz's hero title. They meet a version of Mao's Dad's hand and it states that it is Mao's fault for something before Almaz removes a plug that has been fueling Mao's scar. At the Heart Vault, Almaz reclaims his hero title but turns Mao into a baby. Almaz decides not to help but is soon convinced by Sapphire and returns to Mao's Heart where they meet Savvy Mao. Savvy Mao is protecting Mao from any pain but Raspberyl appears saying that's not the Mao she knows. Saddened that she boycotted class, Mr. Champloo appears and holds a graduation ceremony for her, Asuka and Kyoko (being the first Evil Academy graduates ever). Afterwards, they defeat Savvy Mao and Almaz returns the hero title, returning Mao to normal. Almaz notes the time will come when he is truly a hero.
In Chapter 5, as Mao is regaining his memory from the events of the Heart Vault, he is informed that the campus has undergone a change and sees for himself that Evil Academy has a drastic makeover. He finds out the students are being brainwashed into delinquents and decides to go to the Audio-Visual Room to see for himself. Arriving there, the party meets Gold Knuckle, a senior who has been hypnotizing students by telling simple stories which surprises them considering how he can brainwash students like that. They fight him and at first, Gold Knuckle appears to be holding back and decides to fight seriously. Mr. Champloo appears to their aid, joining the party for the second battle. Afterwards, they find out about a war between the Sophomores and Seniors and head to the Sophomore building. The Sophomore building appears to a war-torn battleground and they meet Master Big Star, the leader of the Sophomores. Mao decides to help after being criticized by Master Big Star for Mao's leadership skills. Near the end of the battle, they meet Salvatore the Magnificent, a Diez Gentlemen and leader of the Seniors. She claims that Mao cannot defeat her and battles them, despite appearing defeated afterwards, she is unfazed by the group. Salvatore tries to order Mao to die by her bullet but Geoffrey appears and takes the bullet for Mao. Angered, Mao nearly unleashes his dark powers when Geoffrey tells him it is not time yet. The chapter ends with Salvatore escaping and Mao seeking power to defeat her.
In Chapter 6, furious having been beaten by Salvatore, Mao seeks to make himself stronger via illegitimate means; so the party ventures back into Mao's heart with the intention of neutralizing any of Mao's "sub-conscious'" that may be holding back his hidden potential. Firstly they happen across some Holy Dragon sub-conscious' who are terrified of the fate that awaits them. Upon their defeat, Mao notes that he doesn't feel much stronger and the party comes to realize that these sub-conscious' are just fledglings and they should instead find the sub-conscious village, where all of the substantial sub-conscious' lurk. Geoffery narrates this segment. The party arrives at the village to find it comprised primarily of Chernabogs, which have the same high-pitched voice and cowardly demeanor of the Holy Dragons. Upon their defeat, Mao exclaims that he feels much stronger and in all subsequent battles, the player has access to Mao's "Vasa Aergun": his ultimate move.
Sapphire and Raspberyl then insist that the party should return to Mao's Heart Vault to check for any new activity. There, the party sees a new figure, who Almaz instantly identifies to be Aurum, the Super Hero who had went missing in the human world. Raspberyl is excited at first but is also the first to question why Aurum is in Mao's Heart. The illusionary Aurum repeatedly asks where the strongest overlord is, confusing the party at first, but Mr Champloo verifies that Aurum must be referring to Mao's father, the current reigning overlord. Aurum keeps asking, eventually claiming that the strongest overlord is Mao. The party defends Mao in their own way, but Mao interprets it as an act of mild betrayal. Nevertheless, the next battle the party must face is against Aurum. After defeating him, Mao claims that it was due to his unlocked potential that the party was able to defeat him. Almaz exclaims that Mao should be able to defeat the Diez Gentlemen now and perhaps even the Overlord- but Sapphire jumps in and notifies the party that Aurum's presence is still felt. Aurum claims that the strongest overlord "is no more". Mao is disdainful that the Super Hero can revive, but Raspberyl is unimpressed and Almaz comments that it seems that Aurum has completely lost the will to fight. Aurum is in turmoil, constantly asking where the next overlord can be found. Mao is sickened by the Super Hero and claims that he has taught him that trust and friends are pointless, seemingly reversing all of the progress that the party had made in trying to open Mao's Heart and heal his trauma. Mr Champloo is the one who realizes this first. The party begin to understand that the super hero must have had a pivotal role in scarring Mao's heart, since he triggered such a vehement reaction from Mao. Almaz sings Aurum's praises, not seeing any way that he could have scarred Mao. Part 1 of chapter 6 ends with Mr Champloo suggesting that the party let the situation progress for now, but when the time is right, they will be the only ones who can support Mao.