WARNING: The following contains spoilers for Season 1, Episode 10 of The God of High School, "oath/meaning," now streaming on Crunchyroll.
While The God of High School anime is largely centered around the titular martial arts tournament, the contest itself in-universe is really a battleground for a much larger and longer-running war. Tournament organizer Park Mujin is hoping that the stresses of these weekly fights will awaken something known as the "Key" in one of its participants. The power of the Key challenges God and Mujin is keen to obtain it. Standing in his way is a mysterious group called Nox, devoted protectors of this God who want the Key destroyed.
While the series has spent the past few episodes strongly suggesting that its protagonist Jin Mori, the renewal taekwondo user, is secretly the Key -- as one would expect -- Episode 10, "oath/meaning," reveals this suggestion is a red herring. The Key's real identity is actually his current rival, Park Ilpyo.
Unlike the teal-haired Jegal, whose megalodon charyeok makes short work of the Nox assassin that Mori left for dead in the last episode, Ilpyo is a fighter cut from a noble cloth. In fact, Ilpyo and Jegal have history: Ilpyo wants to use the wish earned through winning the God of High School tournament to help heal his cousin, who was left without the use of her legs thanks to Jegal. Ilpyo also has history with Mori. Mori's grandpa, a legendary fighter who single-handedly raised Mori and has been captured by Nox for his immense power, pushed Ilpyo toward his antiquated taekkyon fighting style when he was a young child. He also instructed him to "teach Mori a thing or two" if they ever met again.
That's exactly what Ilypo does when he and Mori clash in the arena for the Group A semifinal round. Though Ilpyo's intentions are indeed noble, his taunts to Mori are provocative. A highly observant combatant, Ilpyo has Mori's style memorized and verbally psyches his opponent out by explaining his laundry list of "weaknesses." The two reach an impasse, with Ilpyo countering every one of Mori's attacks while being unable to deal any real damage in retaliation. He needn't worry though, reasoning aloud that Mori will simply tire himself out by placing too much strain on his body.
Little does Ilpyo know that the fire he's about to awaken in Mori will also lead to his own awakening. When Mori finally works out how to catch Ilpyo off-guard -- by harnessing moves borrowed from his friends -- the "tiger"'s disciple is forced to bring out the big guns: his Blazing Cyclone and Hellfire Blade. But Mori's Blue Dragon Tempest, a new upgraded addition to his new Jin Mori Original moveset, eventually overwhelms the taekkyeon user. This is the defeat that unwittingly triggers the Key's arrival. In a spiritual realm, a nine-tailed kitsune approaches the fallen fighter's body, and then, in the physical realm, he's reborn in glowing light with white hair, fox ears and an impossible GP of -1.
Outside of the arena, as the epic supernatural battle that Mujin and Nox's Sang Mandoek have been engaged in draws to a finish, the pair are alerted to Ilpyo's transformation. Mujin is shocked but Mandeok is delighted: "The Key!" This revelation puts Ilpyo firmly on Jegal's hit list, who we know is hunting the Key, as well as Mujin and Nox's, with one hoping to use the Key and the other to destroy it. In short, Ilpyo just became the center of The God of High School's universe.