"God of High School" is an all-styles martial arts tournament for high schoolers from all over Korea. Jin Mori, who lives on his own after parting ways with his grandfather Taejin at a young age, is on his way to the preliminary for his region when he ends up chasing a snatcher. In the midst of his pursuit, he meets Han Daewi and Yoo Mira, two other high schoolers on their way to participate in the preliminary. The only thing on the line is your pride! The only thing you can trust is your fists! Choose any wish, and it will be granted! Such is the power of God! So begins the battle royal featuring the most powerful contenders from all over...

Mori, Daewi, and Mirahave made it through the first preliminary round. With the next round coming up, the three of them talk about their reasons for entering the tournament. Mira says she's hoping to find a strong man who can become the successor to her late father's Moon Light Sword Style and rebuild her family's dojo. On the day of the tournament, one of the favorites to win the tournament, Gang Manseok, faces off against tai chi user Go Gamdo.

Mira faces off against WWD women's pro wrestler Mah Miseon, but her swordfighting can't keep up with Miseon's well-built body and overwhelming strength. Mori faces the risk of being disqualified from the tournament after interfering with the match between Gang Manseok and Go Gamdo. Park Mujin, a National Assembly member and God of High School's sponsor, tells Mori that if he can defeat Commissioner Q in a match, he will be allowed to return to the tournament. Meanwhile, as regional preliminaries continue across Korea, a secretive organization schemes behind the scenes. The "key" to fulfilling their desires turns out to be...

The top four fighters in the preliminary have been decided. With her semifinal match against Daewi drawing near, Mira is suddenly approached by Oh Seongjin, a martial artist and successful businessman, with a marriage proposal. She agrees to marry him in exchange for his promise to restore her family's dojo and spread the Moon Light Sword Style around the world, but marrying him means she must withdraw from the tournament... and Mori and Daewi are not okay with this.

Daewi shows no mercy in his fight against Mira with the goal of getting the money to help his friend, Woo Seungtae, who suffers from an incurable disease. Mori handily defeats his own semifinal opponent, Brazilian jiu-jitsu user Byeon Jaehee, but is angered by Daewi's method of defeating Mira by targeting her injuries. Daewi, meanwhile, learns that Seungtae has taken a turn for the worse and strengthens his resolution even further. Then, amidst all this, Mori and Daewi face each other in the final round.

The national God of High School tournament will be a team battle between teams formed from the top three participants in each regional preliminary. Mira wins the battle for third place, meaning she will compete in the nationals with Mori and Daewi. Mujin explains to the other administrators that this is all part of the search for the one with the potential to be the "Key." At the same time, Mujin puts out a call to The Six, a group of extraordinarily powerful fighters, in order to deal with Nox, another organization searching for the Key.

In the first match of the national tournament, Mori loses his team's opening bout by applying a pressure point he learned from Bongchim of The Six, which renders him immobile. The second bout pits Daewi the tournament's oldest competitor, 38-year-old Jin Pum Kwang, who overwhelms Daewi with powerful attacks acquired through years of hard physical labor. Meanwhile, Commissioner Q is attacked by Drake, a member of Nox, and seriously injured. Q ends up removing his limiter so he can call upon the power of the gods, and the charyeok Joker materializes!

The team led by Park Ilpyo, one of the participants considered a top Key candidate, faces the team led by Gwim Gi. Gwim Gi calls upon his charyeok, Jack the Ripper, but Ilpyo uses his antiquated taekkyon fighting style rather than relying on charyeok. Meanwhile, Daewi is suspended from the competition after interfering in a match and hitting Jugok. Mira scolds him, but Mori seems distracted. Something he sees on Ilpyo's back looks familiar...

After learning that his grandfather, Jin Taejin, has been confined, Mori rushes to set him free. Daewi and Mira await his arrival at the tournament with no idea what's going on. With Mori missing and Daewi suspended, Mira is forced to kick of the team match alone. She struggles against her opponent, Marin, who evades her attacks and counters with her own sword. When he calls it a National Treasure, it begins to glow white, and its true form is revealed...

When he learns of Nox's existence and their role in Jin Taiejin's confinement, Mori swears to win the tournament and save him. But his opponent, Ilpyo, also has a good reason why he can't afford to lose. Four years ago, Seungah's sister and Ilpyo's cousin, Seungyeon, had her leg broken by Jegal and had to give up martial arts for good, and Ilpyo has made up his mind to become cold-hearted for her sake. Meanwhile, Paylong, whose attack on Mori failed, is eliminated... as Jegal wears a cruel smile.

In his battle with Mori, Ilpyo unleashes the charyeok Nine-Tails and awakens as the Key. Mori uses his Blue Dragon Tempest, but Ilpyo stops it easily. The difference in strength between them seems clear, but then, energy suddenly surges forth from Mori's body...

Ilpyo mercilessly beats down Jegal. Just as he's about to deal the finishing blow, Ilpyo sprouts tentacles and ensnares him. With the charyeok Greed, Jegal unleashes the charyeok powers of the others he's absorbed and turns their incredible powers upon Ilpyo. As their battle rages, something changes in the sky over the arena, and it is soon filled with a sword-wielding God and his many followers...

The god that appeared over the arena has been shot down by Jaesan's technique. Mori and the rest have fallen into a huge cave, where they battle against Jegal, who has transformed into a god after absorbing the Key. Mori, Daewi, and Mira face him together, but their attacks don't even reach him, and Daewi is severely wounded protecting Mori from Jegal's vicious onslaught. As the situation grows desperate, a memory that had remained dormant in Mori's mind all this time reawakens...