The tenth episode of "Buried Hearts" kicks off with Dong-ju informing Il-do that he intends to exploit the knowledge of Il-do's attempted murder on him to his advantage. Il-do, intrigued, inquiries if Dong-ju has ever experienced memory loss, to which Dong-ju responds affirmatively. A vivid flashback ensues, depicting Dong-ju contemplating abandoning Il-do to his fate in the ocean after a harrowing rescue attempt. However, in a twist of fate, Dong-ju ultimately decides to save Il-do, confessing later to Won-bae that his motive was rooted in vengeance.
The following day at Daesan, Il-do overhears Dong-ju conversing with Gi-hyeon about convening a board meeting to officially appoint Gi-hyeon as the vice-chairman. Meanwhile, Yeom Jang-seon makes an appearance at Daesan, conveying to Chairman Cha his approval for the long-delayed crude oil import for Daesan Energy. Unbeknownst to Chairman Cha, this decision is orchestrated by The Elder, who instructed Jang-seon accordingly. As a gesture of gratitude, Chairman Cha offers to transfer funds to a Swiss account, oblivious to the fact that Jang-seon has already lost access to it.
Jang-seon's fury intensifies when he discovers Chairman Cha's intention to bestow the vice-chairmanship upon Gi-hyeon. In a moment of solitude, Jang-seon vents his frustration by physically assaulting Il-do. A poignant flashback unfolds, revealing the genesis of Il-do and Jang-seon's tumultuous relationship. It shows a younger Il-do being mercilessly beaten by the police for information, only to be further brutalized by a young Jang-seon who arrives on the scene.
Presently, Il-do is visibly wounded from Jang-seon's attack. Jang-seon interrogates him about why he spared Dong-ju's life, prompting Il-do to confess that Tae-yun's presence had clouded his judgment and led to his error. Il-do reassuringly declares that once he assumes control of Daesan, The Elder will have no further reason to support Dong-ju, setting the stage for an intense power struggle ahead.
At the cozy confines of the bakery, Ji Seon-u unfolds to his mother the dramatic encounter he had with Chairman Cha. Soon after, Deok-hui storms in, returning Seon-u's sneakers with a stern reminder to Ji Yeong-su about her vow to steer clear of Daesan. She casts a dark shadow over their lives, issuing a chilling threat should they dare to collaborate with Dong-ju.
As Deok-hui makes her exit, her gaze falls upon Dong-ju's arrival, prompting her to issue him a stern warning to keep his distance from her family. Dong-ju then engages in a confidential conversation with Ji Yeong-su, laying bare his meticulously crafted plan—a legal marriage between him and Chairman Cha, paving the way for Seon-u to assume his rightful place within the company. With somber expressions, they both impart the truth about Seon-u's father to him.
Dong-ju subsequently reconnects with his hacker ally, Tae-geum, who has worked her magic once again. She has unlocked the vault of Il-do's phone, revealing a treasure trove of information. Among the findings, Dong-ju stumbles upon a poignant photo of young Seong-hyeon, framed alongside Il-do, Sun-ho, and Kang Seong (Dr. Kang's esteemed father). Additionally, Tae-geum has procured a comprehensive list of real estate holdings belonging to Il-do and Jang-seon.
Dong-ju's quest for answers leads him to Yang-chun, still held captive and eager to expose Jang-seon's secrets. Yang-chun reveals the existence of a covert NSA unit known as the Dandelion team, dedicated to spying on and compiling dossiers on the nation's most influential figures, including chaebol leaders and politicians. He whispers of a file implicating Jang-seon, leaving Dong-ju torn between skepticism and curiosity.
Later in the night, Dong-ju encounters the Administrator and unveils a bombshell: the man standing before him is none other than Oh Jung-ho, the former leader of the now-disbanded Dandelion Team. Dong-ju pleads with Jung-ho to exchange the sensitive Dandelion files pertaining to Jang-seon for Yang-chun's safety. Jung-ho, intrigued, instructs Dong-ju to first facilitate a call between him and Yang-chun. Once Dong-ju departs, Jung-ho promptly reaches out to Jang-seon.
Won-bae orchestrates a telephone conversation between Jung-ho and Yang-chun, setting the stage for Jung-ho's next move. In cahoots with Gu-ho, Jung-ho tracks down Yang-chun's whereabouts, intending to eliminate him for betraying the dandelion files. Jung-ho corners Yang-chun and lunges for the kill, but Dong-ju interventions, trapping both adversaries within a makeshift prison of his own devising. Before departing, Jung-ho drops a cryptic hint, hinting at a familiarity with Dong-ju's father that stirs curiosity.
That same evening, Kang Seong forwards a discovered photograph to Deok-hui's phone, as Il-do claims to have misplaced his own. Il-do's demeanor suggests turmoil, while Deok-hui's memory flashes back to the moment she captured that fateful image.
Back at his abode, Dong-ju's mind races over Jung-ho's enigmatic remark. A nostalgic flashback depicts him quizzing his sister about Professor Lee Sup-yung, whom he's glimpsed in a university website photo she was scrutinizing, yet she declines to meet him.
In the present, Dong-ju ventures to visit the professor but is surprised to find Hui-cheol's father, also Jang-seon's brother, in his stead. He conveys that Lee Sup-yung resides overseas and has been informed of Sister Agnes's demise. Moreover, he delivers a stunning revelation to Dong-ju: Sup-yung was not his biological father, nor was Ko You-jin his biological mother; they had adopted him.
Seeking solace and answers, Dong-ju visits Madame Pi, inquiring about his true origins. Madame Pi recounts that Dong-ju simply appeared at Yeon-ju and You-jin's doorstep, as though fate had guided him there. She retrieves a box filled with items found with him—clothes, a Daesan pin, and, astonishingly, the identical photograph Dong-ju once discovered with Il-do's son.
The Elder summons Jang-seon to a meeting, insisting on understanding the rationale behind his decision to initiate an inquiry into his nephew's affairs. It transpires that Jang-seon's intention was to serve as a stark reminder to Lee Cheol-yeong of his considerable prowess and capabilities. Meanwhile, Jang-seon is engaged in a phone conversation with Ji Yeong-su, his tone serious.
Elsewhere, Hui-cheol confronts Eun-nam, inquiring about the real reason for her return. She reveals, with a hint of reluctance, that she faces a penalty for her actions. In a surprising turn, he announces his intention to divorce her, thereby sparing her the financial burden, and urges her to depart at the earliest convenience.
Eun-nam returns home to find Dong-ju waiting for her outside, seated in his car. She informs him, her voice tinged with emotion, that she is on the verge of a divorce. Her gaze then falls upon a photograph in his hand, sparking curiosity. The climactic scene of Buried Hearts Episode 10 unfolds as Dong-ju is left utterly astonished to discover that the man gripping him tightly in the photo is none other than Eun-nam's father.
