How a Korean TV Show Exposed a Serial Husband Killer

In June 2019, a group of seven friends headed to Gapyeong Valley in South Korea for a day of cliff jumping and relaxation. What started as fun ended in tragedy when one man drowned. Initially ruled an accident, the case took a dark turn when his widow appeared on a TV show to complain about insurance. Instead, the program uncovered a chilling murder plot. This blog post explores the shocking story of Lee Eun-hae, dubbed a serial husband killer, and how SBS’s “I Want to Know That” accidentally exposed her crimes.

The Fateful Trip to Gapyeong Valley

Gapyeong Valley, known for its stunning waterfalls and cliff-diving spots, attracts locals seeking adventure. On June 30, 2019, Lee Eun-hae (referred to as “Un” in some accounts) organized the outing. She arrived with her husband, Yoon Sang-yeop (“Sam”), her boyfriend, Cho Hyun-soo (“Joe”), her ex-boyfriend, Lee Jong-ho (“Leo”), Leo’s girlfriend (“Chloe”), her childhood friend (“Yuna”), and Yuna’s boyfriend.

The group dynamics were tense from the start. Un had dated Leo before, but Chloe remained unaware. Meanwhile, Un secretly saw Joe while married to Sam. They spent the day pranking each other, playing games, and eating watermelon. However, as the sun set, three men—Sam, Joe, and Leo—decided on one last cliff dive in the dark. They jumped into the water. Only two surfaced. Sam drowned.

The Mysterious Drowning and Initial Investigation

Witnesses saw Sam struggle in the water. Joe and Leo attempted a rescue, but Sam vanished. Authorities recovered his body later and ruled it an accidental drowning. No autopsy occurred initially, as police saw no foul play.

Un portrayed herself as a grieving widow. She told the media that Sam was her rock, working multiple jobs to support her disabled parents. She claimed he insisted on life insurance for security. Yet, when the insurance company delayed payout due to suspicions, Un turned to SBS’s “I Want to Know That” for help. She wanted to expose corporate greed.

The TV Show That Unraveled the Truth

“I Want to Know That” aired an episode titled “The Last Diving of the Day: Gapyeong Valley Drowning” in 2020. Producers sympathized with Un at first. They aimed to highlight insurance injustices. However, as they dug deeper, inconsistencies emerged.

Footage showed the group bullying Sam all day—pushing him into water despite his poor swimming skills, mocking him. Un flirted openly with Joe and Leo. Reenactments revealed the cliff was too dark for safe jumping, raising questions about the “last dive” suggestion.

Experts noted Sam’s death didn’t match typical drownings. Toxicology later showed zolpidem (a sedative) in his system, possibly from spiked food. The show also uncovered Un’s previous marriages: two ex-husbands died suspiciously—one from a fall, another from poisoning—both with large insurance payouts.

Uncovering the Murder Plot and Motives

The TV episode sparked public outrage. Netizens demanded a reinvestigation. Police reopened the case in 2021. Evidence pointed to murder: Un and Joe had conspired for insurance money. They gaslighted Sam, making him doubt his sanity. Recordings captured Un manipulating him, saying her bad behavior stemmed from drinking.

Joe ran illegal operations, including a trafficking ring. Leo had a criminal record with 28 offenses, including domestic violence. Prosecutors alleged Un lured Sam to the valley, drugged him, and ensured the fatal dive.

Un’s history sealed her fate. Her first husband died in 2009 from a “fall,” netting her insurance. The second died in 2016 from apparent food poisoning. Sam was her third victim, targeted for his $600,000 policy.

The Trial, Sentencing, and Aftermath

In 2022, authorities arrested Un and Joe. The trial revealed gaslighting tactics: Un isolated Sam, controlled his finances, and humiliated him publicly. Prosecutors played voice recordings of her emotional abuse.

The court found Un guilty of murder, sentencing her to life in prison. Joe received 30 years for aiding. Leo faced charges, but prosecutors pursued him less aggressively.

Read more: Peter Keller: Who Vlogged His Murder Plan for 8 Years

In prison, Un shockingly penned letters to Cho Hyun-soo (another criminal from the Nth Room case), consoling each other like mentors. The initial police investigator apologized publicly for mishandling the case.

The Chilling Prison Letters of Lee Eun-hae

Lee Eun-hae, the woman at the center of South Korea’s infamous Gapyeong Valley murder case, has become synonymous with calculated cruelty and insurance fraud. Convicted in 2022 of orchestrating her husband Yoon Sang-yeop’s drowning for an 800 million KRW ($600,000) payout, she was sentenced to life in prison. But behind bars, Eun-hae’s story didn’t end—it evolved through a series of prison letters that reveal her unyielding denial, manipulative pleas for sympathy, and an astonishing correspondence with one of Korea’s most reviled criminals: Cho Ju-bin, the mastermind of the Nth Room sex trafficking scandal. These letters, pieced together from media exposés and court revelations, offer a window into a mind that refuses accountability, even as public outrage mounts. In this deep dive, we explore the contents, context, and fallout of Eun-hae’s prison writings.

Letters to the Media: A Desperate Bid for Innocence

While awaiting trial and after her conviction, Eun-hae turned to the media with handwritten letters that doubled as a public relations campaign. In one particularly poignant exchange, revealed during MBC’s 2024 true crime series She Killed, Eun-hae wrote directly to the production team.

“Even if it’s an uncomfortable truth, I’ve decided to tell my story,” she began, framing her words as a courageous confession. She vehemently denied murdering her husband, insisting the cliff dive was an “unintentional accident.” According to her account:

• Yoon “jumped out voluntarily” into the dark waters of Yongso Falls.
• She “threw everything she could,” including a lifeboat, after glancing back and realizing he hadn’t resurfaced.
• Yoon was a strong swimmer with “no fear of water”—she claimed to have seen him swim confidently in a pool.
• The day’s tensions stemmed from a private argument over “sexual intercourse” with her husband, which she downplayed by “relaxing her mood” through play with her boyfriend Cho Hyun-soo and Yoon.

Eun-hae painted herself as a victim of circumstance, not a perpetrator. Her father, in a heartbreaking twist, echoed her claims during the broadcast, expressing belief in her version of events. These letters weren’t just defensive; they humanized her, tugging at sympathies by emphasizing Yoon’s supposed independence and her own remorse. Yet, prosecutors dismissed them as classic gaslighting—echoing the emotional abuse she’d inflicted on Yoon during their marriage, where recordings captured her blaming her cruelty on alcohol: “When I drink, I turn into someone else and treat those closest to me really badly.”

Critics argue these writings were a calculated extension of her courtroom strategy. During the 2022 trial, Eun-hae maintained her innocence, lamenting the verdict as a lost “opportunity to prove” herself. Her letters to MBC reinforced this narrative, blending vulnerability with deflection to sway public opinion.

The Shocking Correspondence with Cho Ju-bin

If Eun-hae’s media letters were a solo act of self-preservation, her exchanges with fellow inmate Cho Ju-bin (also known as Jo Joo-bin) exposed a darker alliance. Cho, sentenced to 42 years for running the Nth Room—a depraved online blackmail ring targeting over 260 victims, including minors—reached out to Eun-hae shortly after her 2021 arrest. Both were housed at Incheon Detention Center, where inmates can exchange letters through the facility’s system—a practice Cho exploited due to his prior detentions.

Revealed in October 2022 by former prosecutor Jo Jae-bin during an SBS interview, the letter from Cho was no idle chit-chat. It offered brazen legal advice: “Do not cooperate with the prosecution’s investigation and refuse to testify.” As someone already infamous from his 2020 trial, Cho positioned himself as a “mentor,” presumptuously guiding the newcomers. Eun-hae and her accomplice, Cho Hyun-soo (no relation to the Nth Room perpetrator), heeded the counsel. They stonewalled investigators—Eun-hae demanded a lawyer for every questioning, while Hyun-soo avoided incriminating statements. The pair even coordinated alibis by swapping interrogation details via letters, turning the detention center into a strategy hub.

Public reaction was one of visceral horror. Netizens flooded social media with outrage, dubbing the duo “two of a kind” and decrying Cho’s audacity in playing advisor. Comments ranged from “This guy is even doing this kind of thing” to concerns for Eun-hae’s young daughter, left in the wake of her mother’s crimes. Lawyer Jo Jae-bin himself admitted shock: “I thought, ‘This guy is even doing this kind of thing.'” The letters highlighted a prison subculture where notoriety breeds unlikely bonds, but they also underscored Eun-hae’s pattern of seeking enablers—much like her tangled web of lovers and accomplices outside.

While full texts remain sealed, leaks suggest the tone was conspiratorial and self-pitying, with Cho consoling Eun-hae over their shared “injustices.” This wasn’t romance but a mutual pity party among monsters, as one commenter put it: “Poor baby, the world is so mean to us.”

The Broader Implications: Gaslighting from Beyond the Grave?

Eun-hae’s letters extend her legacy of manipulation. In court, gaslighting was a central theme—prosecutors played recordings of her eroding Yoon’s confidence, isolating him financially and emotionally. Her prison writings mirror this: denying agency in Yoon’s death while portraying him as fearless, even as evidence showed he couldn’t swim and begged for help during the dive. Toxicology confirmed sedatives in his system, likely from food she prepared.

These documents also spotlight prison vulnerabilities. How does a system allow such exchanges? Reforms followed: In 2023, the Seoul High Court upheld Eun-hae’s life sentence, citing her lack of remorse as evidenced by her unyielding denials. Cho Ju-bin’s meddling drew fresh scrutiny to his own case, where criticism already swirled over his prison blog.

For true crime enthusiasts, Eun-hae’s letters are a masterclass in deflection—a final act from a woman who turned love into a ledger. They remind us that evil doesn’t repent; it rewrites. What do you make of her claims? Drop your thoughts in the comments, and stay tuned for more explorations of Korea’s darkest cases.