5 Shocking Revelations About Sun And Jin's Affair: The Definitive Truth On Whether Sun Cheated On Jin

The question of whether Sun-Hwa Kwon cheated on Jin-Soo Kwon remains one of the most contentious and heartbreaking plot points in the history of the iconic television series, Lost. As of this December 2025 analysis, the answer is a definitive and complicated 'yes,' but the full context of Sun's betrayal is far more complex than simple infidelity. The affair was a pivotal moment, not just for the couple, but for the entire narrative of Oceanic Flight 815 survivors, exposing the deep-seated secrets and lies that plagued their marriage long before they crashed on The Island.

This article dives deep into the timeline, the identity of the other man, the shocking revelation, and the ultimate truth about their daughter, Ji Yeon, to provide a fresh, comprehensive understanding of the most tragic romance on television. Their story is a masterclass in character development, moving from a toxic, abusive dynamic to one of the most enduring love stories in the show, yet it’s forever marked by this pre-Island secret.

The Complete Biography and Timeline of Sun-Hwa Kwon and Jin-Soo Kwon

To fully grasp the weight of Sun’s actions, it is essential to understand the characters and the oppressive environment of their life in South Korea, particularly under the thumb of Sun’s powerful and ruthless father, Mr. Paik.

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• Sun-Hwa Kwon (Yunjin Kim): The daughter of the wealthy and powerful Korean magnate Mr. Paik. She is intelligent, fluent in English (a secret she initially kept from Jin), and yearned for independence and a genuine, loving relationship. Her affair was an act of rebellion against her controlling marriage and father.
• Jin-Soo Kwon (Daniel Dae Kim): A poor fisherman who married Sun, ostensibly for love, but was quickly forced to work as an enforcer and thug for Mr. Paik's criminal empire. He became emotionally distant, abusive, and oppressive towards Sun, believing he was protecting her through his obedience to Paik.
• The Marriage: Their marriage was arranged and quickly devolved into a transactional and miserable partnership. Jin was infertile (a fact he was unaware of), which added immense pressure as Mr. Paik demanded a grandson.
• The Affair: Occurred before the crash of Oceanic Flight 815, specifically during a period of extreme emotional distance from Jin.
• The Island Life: They spent the early days on The Island estranged, with Sun secretly learning English and planning to leave Jin. Their reconciliation began when Jin saved Sun from an attempted kidnapping.
• The Death: Sun and Jin tragically died together in Season 6, Episode 14 ("The Candidate"), drowning in the submarine after being trapped by the explosion, fulfilling their shared destiny.
• The Flash-Sideways: They were reunited in the "Flash-Sideways" reality in the series finale, recognizing their profound bond and moving on together.

Revelation 1: The Other Man Was Sun's English Tutor, Jae Lee

The man Sun cheated with was Jae Lee, her English tutor. This affair was detailed in the Season 2 flashback episode, "The Glass Ballerina." The relationship was a profound emotional and physical escape for Sun from her suffocating marriage to Jin.

Jae Lee represented the life Sun desperately wanted: one of freedom, intellectual connection, and genuine affection, all the things she felt Jin had stripped away from her. The affair was not a casual fling; it was a desperate reach for happiness. Tragically, the affair had dire consequences.

• The Discovery: Mr. Paik discovered the infidelity.
• The Consequence: Paik manipulated Jin into believing Jae Lee had stolen from him. Jin was then ordered to deliver a brutal message: he was to kill Jae Lee.
• The Twist: Jin, unable to commit murder, instead severely beat Jae Lee and told him to leave the country. However, Jae Lee later committed suicide by jumping from his balcony, an event Jin was forced to witness, forever scarring him.

This sequence of events highlights how the affair was merely a symptom of the larger disease in their marriage, which was controlled by the machinations of Mr. Paik, turning Jin into a monster and Sun into a desperate woman.

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Revelation 2: The Truth Was Exposed by Juliet Burke

One of the most dramatic confrontations on The Island occurred when the truth about the affair was finally revealed to Jin. This shocking moment was orchestrated by Juliet Burke, a member of the Others, in the Season 3 episode "Ji Yeon".

Juliet's motivation was complex. She was working for Ben Linus and Charles Widmore, and her primary goal was to get Sun and Jin off the Island. She knew that by exposing Sun's infidelity, she would create an irreparable rift that would force Jin to leave, believing his wife was in danger and that the baby was not his.

• The Lie: Juliet told Jin that Sun had been unfaithful and that the baby she was carrying was Jae Lee's, not his.
• The Reaction: Jin was devastated and furious, leading to a physical confrontation between Sun and Juliet, where Sun slapped her. This revelation fractured their newly repaired relationship on the Island.
• The Strategy: Juliet's move was a calculated act to manipulate the couple, using their deepest secret and fears—the baby's paternity—as leverage to get them to the freighter and ultimately off the Island.

Revelation 3: The Island Cured Jin and He IS Ji Yeon's Father

The most crucial and redemptive twist in the entire storyline is the definitive resolution of the baby's paternity. For a long time, Sun feared the baby, named Ji Yeon, was Jae Lee's, especially after a test in Season 2 confirmed Jin was infertile back in Korea.

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However, the Island, being a place of miracles and anomalies, intervened. In Season 3, after a trip to the Staff station with Juliet, Sun learned her exact date of conception. This date proved that she became pregnant *after* the crash of Oceanic Flight 815, meaning the child was conceived on The Island.

• The Definitive Answer: Jin is Ji Yeon's biological father.
• The Island's Role: The Island's unique properties cured Jin of his infertility, allowing him to conceive a child with Sun. This reveal completely changes the context of the affair, as the baby was a true symbol of their renewed love and the Island's power, not a permanent reminder of Sun's betrayal.

This revelation was the ultimate act of forgiveness and reconciliation for the couple, proving that their true love was stronger than the lies and the oppressive life they led before the crash. Their daughter, Ji Yeon, became the most important person in both of their lives, providing the motivation for their actions off the Island.

Revelation 4: Critical Perspectives on Sun's Betrayal

While Sun’s affair is often viewed as a simple act of infidelity, critical analysis and fan discussions over the years have consistently framed it within the context of her abusive marriage.

• The Context of Oppression: Sun was trapped. Jin was emotionally absent and physically oppressive due to his role as Mr. Paik's enforcer. Her affair was a desperate attempt to regain control and find emotional validation.
• The Shared Guilt: Many viewers and critics argue that both Sun and Jin were "cheating" on each other. Sun cheated physically, while Jin cheated on the promise of their love by becoming his father-in-law's monster and hiding his true nature and actions from Sun. The marriage was built on a foundation of mutual deceit and fear.
• The Redemption: The Island stripped away the lies, allowing them to communicate and fall in love with the people they truly were, not the roles they were forced to play. The affair, while painful, was the catalyst that forced the truth out and allowed their true, deeper bond to emerge.

In the end, the affair was a necessary evil. It was the breaking point that forced Sun to plan her escape and, ultimately, led to the confrontation that allowed them to truly reconcile and realize their love for each other before their tragic end.