Jeong-yo’s return as a conductor in Four Hands creates an immediate question.
How did a young pianist who disappeared after suffering a devastating right-arm injury eventually return to the classical music world as a conductor?
His injury can explain why he stopped playing the piano.
But it does not explain what happened next.
Someone may have helped Jeong-yo rebuild his life.
And one character now deserves much more attention:
Yoon Seon-joo, the chairwoman and Kang Seung-woon’s wife.
There is not yet enough evidence to say that Seon-joo definitely helped Jeong-yo become a conductor.
However, several pieces of the story make the theory worth examining.
Jeong-yo’s Injury Explains Only Half the Story
We now have two very different versions of Jeong-yo.
The first is the young piano genius.
The second is the man who returns as a conductor.
Between those two versions is a missing period that the drama has not fully explained.
We know Jeong-yo disappeared.
We also learn that his right arm was seriously injured, leaving him unable to continue playing the piano as before.
But that creates another problem.
A serious injury does not automatically turn a pianist into a conductor.
Conducting requires education, training, opportunities, professional connections and, most importantly, someone willing to open the first door.
So the real mystery may not simply be:
Why did Jeong-yo stop playing piano?
It may be:
Who gave Jeong-yo a second chance in music?
Why Yoon Seon-joo Is So Important
Yoon Seon-joo should not be viewed only as Kang Seung-woon’s wife.
She is also the chairwoman, which gives her a position of influence separate from her husband.
That distinction matters.
Kang Seung-woon represents musical authority.
Seon-joo potentially represents institutional power—the ability to support someone, create opportunities and influence what happens behind the scenes.
If Jeong-yo lost his future as a pianist but still possessed extraordinary musical ability, someone with both resources and an understanding of the classical music world would have been in a position to help him redirect that talent.
Seon-joo fits that possibility.
But again, this remains a theory until the drama explicitly confirms it.
Her Departure From the House May Matter More Than It Seems
Another detail makes the theory more interesting.
Seon-joo leaves the household.
At first, this can be understood primarily through her relationship with Kang Seung-woon and the conflict inside the family.
But Four Hands repeatedly connects family decisions with musical consequences.
That makes it reasonable to ask whether her departure also intersects with Jeong-yo’s missing years.
What did Seon-joo know?
Did she know where Jeong-yo had gone?
Did she know about his injury?
And if she discovered that a gifted young pianist could no longer use his right arm normally, did she simply watch his musical life end?
Or did she decide to help him find another path?
The drama has not answered those questions yet.
But Jeong-yo’s return as a conductor makes them much harder to ignore.
Why Would Seon-joo Help Jeong-yo?
If the theory is correct, her motivation does not necessarily have to be mysterious or sinister.
It could actually be very human.
Jeong-yo was an exceptional young musician whose future suddenly collapsed.
If Seon-joo believed that his musical gift remained intact despite his physical injury, she may have refused to accept that his career had to end with the piano.
There is also a deeper possibility.
The adults around Bi-o and Jeong-yo made choices that had enormous consequences for both boys.
Kang Seung-woon chose Jeong-yo for an important musical opportunity rather than favoring his own grandson.
Musically, that decision may have been fair.
Emotionally, however, the rivalry between Jeong-yo and Bi-o became increasingly destructive.
If Seon-joo witnessed the consequences, helping Jeong-yo later could have been partly motivated by responsibility.
Not because she caused his injury—we have no confirmation of that—but because she may have felt that the adults could not simply abandon him after everything that happened.
Did Kang Seung-woon Deliberately Remove Jeong-yo?
This is where another viewer theory becomes much more controversial.
Some viewers have speculated that Kang Seung-woon may have intentionally removed Jeong-yo from the competition or musical path in order to give Bi-o a better chance.
It is an explosive theory.
It is also not confirmed.
In fact, there is an obvious contradiction.
Earlier, Seung-woon appears willing to choose Jeong-yo over his own grandson when he believes Jeong-yo is musically superior or more appropriate for a particular opportunity.
That does not naturally fit the behavior of a grandfather determined to guarantee Bi-o’s victory at any cost.
If anything, Seung-woon’s earlier choices suggest that he values musical judgment enough to hurt Bi-o rather than simply favor him.
So the theory that he suddenly decided to eliminate Jeong-yo solely to make Bi-o number one requires much stronger evidence.
The drama may eventually provide that evidence.
But it has not done so yet.
Seung-woon and Seon-joo May Represent Two Different Responses
There is another way to interpret the couple.
Perhaps Seung-woon and Seon-joo respond differently to what happens to the two young musicians.
Seung-woon is obsessed with music at the highest level.
He recognizes talent, judges musicians harshly and appears willing to make painful decisions based on artistic standards.
Seon-joo may represent a different perspective.
She may be more concerned with what happens to the person after the musical judgment has been made.
If Jeong-yo’s piano career was destroyed, Seung-woon might see a pianist who can no longer perform.
Seon-joo might see a musician who still needs a future.
If that contrast becomes part of the drama, it could explain why Jeong-yo eventually returns not as the pianist Seung-woon once recognized, but as a conductor who found another way to use his talent.
Becoming a Conductor Would Require Years of Reconstruction
This is another reason the missing years matter.
Jeong-yo cannot simply disappear as a pianist and suddenly reappear as a convincing conductor without a major transformation.
He would need to rebuild his understanding of music from a different perspective.
As a pianist, his body directly produced the sound.
As a conductor, he would have to communicate musical ideas through gesture, interpretation and leadership.
He would also need access to orchestras, mentors and professional opportunities.
That makes the identity of the person—or people—who supported him extremely important.
If Seon-joo helped arrange that transition, her role in Four Hands could be much larger than viewers initially expected.
She would not merely be the chairwoman or Seung-woon’s wife.
She would become one of the key people responsible for Jeong-yo’s second musical life.
The Right-Arm Injury Could Have Changed Seon-joo Too
Jeong-yo’s injury obviously transforms Jeong-yo.
But it may also transform the adults around him.
Imagine the situation from Seon-joo’s perspective if the theory proves correct.
A young man with extraordinary talent is suddenly unable to pursue the future everyone expected.
The rivalry between him and her grandson has already caused emotional damage.
Her husband has played a major role in shaping that rivalry through his musical choices.
And now Jeong-yo has disappeared from the piano world entirely.
Helping him become a conductor could therefore represent more than generosity.
It could be Seon-joo’s attempt to repair something that the adults failed to protect.
That would also give her departure from the household much greater dramatic meaning.
And What Would This Mean for Bi-o?
This is where the theory becomes especially powerful.
Imagine Bi-o discovering that Jeong-yo has returned.
For years, Bi-o measured himself against Jeong-yo.
He wanted to defeat him at the piano.
He wanted the recognition Jeong-yo seemed able to receive naturally.
Then Jeong-yo disappeared.
If Bi-o eventually learns that his own grandmother—or the woman at the center of his family—helped Jeong-yo rebuild his musical life, the emotional impact could be enormous.
From Seon-joo’s perspective, she may simply have saved a gifted musician.
From Bi-o’s perspective, it could feel like another member of his family chose Jeong-yo over him.
That would reopen the deepest wound in their rivalry.
And this time, the competition would no longer be pianist versus pianist.
It could become something much more complicated:
Bi-o at the piano, Jeong-yo on the conductor’s podium, and the same family standing between them.
Could Jeong-yo’s Conducting Debut Be Connected to Seon-joo?
This is now one of the details worth watching closely.
When Jeong-yo appears as a conductor, viewers should pay attention not only to him but also to the people around him.
Who arranged the opportunity?
Who already knows him?
Who is surprised to see him?
And who is not surprised?
A character’s reaction could reveal more than dialogue.
If Seon-joo already knows about Jeong-yo’s conducting career before the rest of the family discovers it, that would strongly support the theory that she was involved during his missing years.
If she is just as surprised as everyone else, the theory becomes much weaker.
That is why her reaction to Jeong-yo’s return may become one of the most important clues.
What We Know and What Is Still Theory
At this stage, it is important not to mix confirmed story information with speculation.
What the story establishes is that Jeong-yo’s path changes dramatically: the gifted pianist disappears, suffers a serious problem involving his right arm, and later returns to the musical world in a different role.
What remains unresolved is exactly how that transformation happened.
The idea that Yoon Seon-joo helped him become a conductor is therefore best understood as a viewer theory.
Likewise, the idea that Kang Seung-woon deliberately pushed Jeong-yo aside to help Bi-o win should not yet be treated as established fact.
Both theories may become important.
Both could also be wrong.
That uncertainty is precisely what makes the missing period in Jeong-yo’s life so interesting.
Final Thoughts
Jeong-yo’s right-arm injury explains why the piano disappeared from his life.
It does not explain how music returned.
That may be the next mystery Four Hands is preparing to answer.
And Yoon Seon-joo is one of the strongest characters to watch.
As chairwoman, she potentially has the resources and influence to help Jeong-yo.
As Kang Seung-woon’s wife, she is close to the family conflict that shaped Bi-o and Jeong-yo.
And as someone who leaves the household, she may have a story during Jeong-yo’s missing years that viewers have not yet seen.
So the key question is no longer only:
Who hurt Jeong-yo?
There is another question that may prove just as important:
Who saved Jeong-yo’s music after he could no longer play the piano?
If the answer is Yoon Seon-joo, then her departure from the family may not have been the end of her role.
It may have been the beginning of Jeong-yo’s second life.