Four Hands: A method where two people play on a single piano.

Kang Bio and Choi Jeongyo start in conflict over an unwanted Four Hands arrangement, but as they introduce each other to experiences they've never had in their respective worlds, they begin to connect.

Four Hands is more than just a musical term; it is a 'means through which two rivals come to understand one another and create music together.'

In a world where art has become worthless, this is the story of geniuses who threw their entire lives into the piano.

An era where the value of art has hit rock bottom. An era where total immersion in art with all one's heart is often dismissed as mere foolish obsession. An era where the only wise choice is what can be converted into money, and even pure art is evaluated by its 'price' rather than its 'value.'

Yet, even so, we secretly admire artists who throw their everything to reach a true state of mastery, sending respect and praise to their pure passion. Even if that passion shakes their lives to the core and eventually wounds them, there were artists who threw their entire existence away for the sake of the most perfect art.

This is a story about artists who staked their everything for a single piece of music, a single world, and a single person. A boy who longed for genius, and another genius who shook that longing. The two boys, who understood each other most deeply, expanded each other's worlds through a brilliant friendship, but the desire to be the best and the uncompromising obsession with art eventually hurt each other more than anyone else, creating a desperate rift.

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One day, at the suggestion of a mentor who wants Bio and Jeongyo to grow, the two perform a Four Hands piece. At first, they aren't even in sync due to each other's weaknesses, but as Jeongyo opens up about his complexes and Bio compensates for them, the two gradually grow closer.

Ten years ago, the two participated in a world competition together. Unlike Bio, who headed to the venue first, the car Jeongyo was in headed for a forest instead of the venue for unknown reasons. Jeongyo tried to escape but was eventually shot and disappeared beneath a pond.

Due to Jeongyo's disappearance, Bio participated in the competition alone and won, but as soon as he realized Jeongyo hadn't arrived, he immediately went looking for him. He spent the next five years searching for Jeongyo, but could not even confirm if he was alive.

Then one day, Bio happens to spot a conductor while traveling. A man conducting the very piece he and Jeongyo had played together in high school. It was Jeongyo, whom he had thought was dead.

Jeongyo, who claims to have lost his memory due to the shooting nine years ago, pretends not to remember Bio. He believed Bio was the one who ordered his assassination and deliberately kept him close for revenge. However, the person behind the incident was not Bio, but Bio's mother.

Jeongyo chooses Bio as the soloist for his first work, <Nemesis>, and forces him through grueling practice. He intended to make Bio give up the piano, but Bio endures until the end, finally completing the performance Jeongyo wanted.

And on the stage of the <Nemesis> premiere, Bio falsely confesses that he was the one who ordered Jeongyo's death in the past. It was to turn Jeongyo's suspicion and anger toward himself. Bio is arrested, but afterward, Jeongyo learns that Bio was not the one who tried to harm him.

With the long-standing misunderstanding resolved, the two play Four Hands once more. However, Jeongyo's hand was slowly becoming paralyzed as an aftereffect of the shooting, and after that final performance, he leaves Bio's side for a foreign country.

Three years later, Bio no longer stands on big stages. Instead, he visits hospitals and child welfare facilities to play the piano for children. Then one day, he releases a video of himself playing <Nemesis> with the hope of reaching Jeongyo.

Sometime later, a letter arrives for Bio.

And in a small cathedral in Czechia.

The sound of children singing echoes, and a man is conducting in front of them.—

Another person watches that back.

Their music begins again.