Spoiler Warning: This article contains major spoilers for Four Hands, Two Sonatas Episode 4.
Why did Kang Pi-o collapse at the end of Four Hands, Two Sonatas Episode 4?
The episode ends with one of the drama’s most alarming scenes so far.
After pushing Jeong-yo away and shutting himself inside his room, Pi-o stops responding. His mother, Kang Ji-hye, eventually goes inside and finds him lying unconscious.
But Episode 4 does not clearly reveal a specific medical diagnosis for Pi-o’s collapse.
Instead, the drama spends the entire episode showing us something else:
Pi-o has been breaking down emotionally under years of pressure, and Jeong-yo’s arrival finally pushes that pressure to a crisis point.
What Happened to Pi-o at the End of Episode 4?
Before Pi-o collapses, several parts of his life begin falling apart at the same time.
Pi-o has spent years training as an elite pianist while carrying enormous expectations from his family.
His mother expects him to succeed.
He desperately wants recognition from his grandfather, Kang Seung-woon.
And then Choi Jeong-yo enters his life.
At first, Jeong-yo actually helps Pi-o rediscover something he had almost forgotten:
the joy of playing music.
But the same friend soon becomes the person who threatens Pi-o’s entire sense of identity.
Pi-o Has Been Under Pressure for Years
To understand the collapse, we need to understand Pi-o’s childhood.
Pi-o did not begin playing the piano simply because he wanted trophies.
As a child, music brought him genuine happiness.
But over time, that relationship changed.
Practice became connected to competition.
Competition became connected to expectations.
And success became connected to approval.
Pi-o learned that being excellent was not enough.
He had to keep winning.
That is especially important because his mother, Ji-hye, has placed enormous expectations on him.
By Episode 4, Pi-o is no longer simply a perfectionist.
He looks like someone who has spent years carrying a life designed by the adults around him.
Why Grandpa Choosing Jeong-yo Hurts Pi-o So Much
Then comes the emotional blow that Pi-o is least prepared for.
His grandfather recognizes Jeong-yo’s musical ability.
For another pianist, this might simply create professional jealousy.
For Pi-o, it is much more personal.
Pi-o has spent years wanting his grandfather’s recognition.
Kang Seung-woon is both his grandfather and the musician whose approval means almost everything to him.
Then Jeong-yo arrives and receives the attention Pi-o has been chasing.
That creates a terrifying question inside Pi-o:
What if all my years of work still cannot give me what Jeong-yo seems to possess naturally?
This is why Pi-o’s jealousy cannot be explained simply as competition between two talented pianists.
Jeong-yo threatens the way Pi-o understands his own value.
Jeong-yo Is Both Pi-o’s Friend and His Greatest Threat
This is what makes their relationship especially painful.
Jeong-yo is not someone Pi-o simply hates.
In fact, Jeong-yo had started becoming one of the few people around whom Pi-o could experience music differently.
They practiced together.
They began understanding each other.
And Pi-o gradually opened himself to Jeong-yo.
That makes the rivalry worse, not easier.
If Jeong-yo were merely an enemy, Pi-o could simply try to defeat him.
Instead, the person who helps Pi-o rediscover the happiness of music becomes the same person who triggers his deepest insecurity.
Pi-o wants Jeong-yo beside him.
But he is also terrified of standing next to him.
Why Does Pi-o Push Jeong-yo Away?
By the end of Episode 4, Pi-o feels betrayed and overwhelmed.
Jeong-yo tries to reach him, but Pi-o refuses to listen and pushes him away before going into his room.
That reaction is important.
Pi-o is no longer dealing with only one problem.
His feelings toward Jeong-yo, his grandfather’s judgment, his mother’s expectations, his fear of failure and his uncertainty about music are all colliding at once.
The drama then cuts to the disturbing final image:
Pi-o lying unconscious in his room.
Did Pi-o Collapse Because of Stress?
Episode 4 does not yet give viewers a confirmed medical explanation.
So it would be premature to diagnose exactly what happened to him.
However, the storytelling strongly connects his collapse with the enormous emotional and psychological pressure surrounding him.
Throughout the episode, Pi-o appears increasingly exhausted and overwhelmed.
The collapse therefore works not only as a cliffhanger but also as a physical representation of what has been happening internally.
Pi-o has spent years trying to remain perfect.
Episode 4 may be the moment when he can no longer maintain that perfection.
Pi-o’s Mother Is Important to Understanding the Scene
There is another layer to the ending.
The person who discovers Pi-o is his mother.
Ji-hye has spent years pushing her son toward achievement, while her own complicated relationship with Kang Seung-woon appears to influence how she raises Pi-o.
That makes the ending especially significant.
The mother who has demanded so much from Pi-o is finally forced to see what that pressure may be doing to him.
And that could become important in the episodes ahead.
Will she recognize that Pi-o is suffering?
Or will she blame Jeong-yo for what happened?
The ending of Episode 4 leaves that conflict wide open.
The Collapse Is About More Than Jeong-yo
It would be easy to say:
Pi-o collapsed because of Jeong-yo.
But that would oversimplify the story.
Jeong-yo did not create Pi-o’s problems.
He exposed them.
The pressure was already there.
The need to be perfect was already there.
The desperate desire for his grandfather’s approval was already there.
And his mother’s expectations were already there.
Jeong-yo simply became the person who forced Pi-o to confront a possibility he had never been prepared to accept:
Someone else could be extraordinary without following Pi-o’s path.
What Will Happen to Pi-o in Episode 5?
Episode 4 does not yet tell us exactly what happens after Pi-o is found unconscious.
That makes his condition one of the biggest questions heading into Episode 5.
But the more important question may not be whether Pi-o physically recovers.
It may be whether anything changes after he does.
Will his mother continue pushing him?
Will Pi-o blame Jeong-yo?
Will his grandfather reconsider the way he treats him?
And can Pi-o return to the friendship that had briefly helped him enjoy music again?
The collapse may mark the point where Pi-o and Jeong-yo’s friendship begins turning into the painful rivalry we have already been warned about.
Four Hands Episode 4 Ending Explained
So why did Pi-o collapse?
The drama has not yet confirmed a specific medical cause.
But Episode 4 deliberately shows Pi-o reaching his emotional limit after years of perfectionism, family expectations, competition and his growing insecurity toward Jeong-yo.
That distinction matters.
Jeong-yo may be the immediate trigger for Pi-o’s emotional crisis, but he is not the root cause.
Pi-o has been carrying this pressure for years.
And perhaps the most tragic part of Four Hands, Two Sonatas is that the person who helped Pi-o rediscover why he loved music may now become the person Pi-o believes is taking everything away from him.
More Four Hands, Two Sonatas Explained
Read Why Is Pi-o Jealous of Jeong-yo? Grandpa’s Choice Explained to understand why Jeong-yo’s talent affects Pi-o so deeply.
You can also read Pi-o vs Jeong-yo: Who Is the Better Pianist? for our analysis of the drama’s “calculation vs instinct” conflict.
And read Jeong-yo’s Family Secret Explained for the major Episode 4 revelation about his father.