Episode 13 of "Bad-Memory Eraser" commences with a bombshell: photos of a tumultuous past are splashed across the internet, igniting whispers that Shin had nefarious intentions towards Gun, even attempting his life. Gun and Hong, aghast, beseech the police for assistance in locating Shin, but their pleas are met with reluctance. Undeterred, Gun insists they must pursue him for attempted murder, the gravity of the situation etched on his face.
Meanwhile, Shin's solitude is shattered by a chilling voicemail from an elusive stalker, a sinister ultimatum echoing through the airwaves: emerge from hiding or face the consequences of your secrets being exposed to the world.
Gun, poring over the dashcam footage from their fateful reunion night, witnesses a haunting replay of events. There, Shin's leap from the bridge and Gun's desperate grasp to save him are frozen in time. A memory flashback unfolds, revealing a heated exchange between the brothers, their voices laced with emotion as they grapple with the weight of sacrifice and identity. Shin's words, heavy with anguish, confess the stifling burden of being Gun's shadow, while Gun's retort, sharp and resolute, urges him to break free. As Gun storms off, Shin's despair culminates in a leap, only to be met with Gun's steadfast hand, a fleeting moment of solace amidst the chaos.
But in a desperate bid to hold on, Gun stumbles, his head crashing against the unforgiving rail. Shin, now the rescuer, frantically performs CPR, tears streaming down his face, consumed by guilt.
Back at their abode, Mr. Lee's confession cuts deep, revealing a father's regret for pushing Shin to the brink, his financial ruin leading to a chain of events that saw his son burdened with responsibilities beyond his years.
Elsewhere, Ju-yeon's unwavering concern for Gun prompts her to task Han with keeping tabs on him. Yet, Sae-yan, still searching for her elusive father, wonders at Ju-yeon's persistent efforts to draw her towards Gun, her curiosity piqued. Ju-yeon, quick on her feet, redirects her friend's attention back to the search, their quest leading them to a web of half-truths and fleeting leads.
As for Shin, his journey finds him on a secluded beach, where he procures a camping kit from a genial couple. However, fate seems bent on testing him further as he stumbles into a confrontation with unruly youths, his wallet inadvertently exchanged in a misguided attempt to aid them. The tennis association's wrath looms large, threatening Shin with expulsion if he fails to surface within two days. Gun, his determination unshaken, vows to bring his brother home, no matter the cost.
Next, we witness a heart-wrenching encounter as Sae-yan comes face to face with the man she believed to be her father. She embraces him, tears streaming down her face, eliciting a compassionate gaze from him. However, his subsequent confession shatters her world: he is not her biological father; he had been hired to play the role. Outside, her mother, Mrs. Jeon, and Ju-yeon stand waiting, the former revealing that she has already submitted Sae-yan's resignation, a decision Ju-yeon strongly opposes. Mrs. Jeon explains her actions as an attempt to spare everyone the burden of painful memories, but Sae-yan interrupts, imploring her mother to leave her be. As she storms off, Ju-yeon admonishes Mrs. Jeon for deceiving her and rushes after Sae-yan.
Elsewhere, Shin finds himself shivering in the cold, resorting to hoarding blankets and reaching out to Ju-yeon for assistance via a payphone. His embarrassment gets the better of him, causing him to abruptly end the call, but Ju-yeon's detective skills lead her straight to his location. Meanwhile, disaster strikes when Shin's delinquent acquaintances stumble upon his ID and post it on social media, prompting Gun to rush to the beach, hot on their heels.
Ju-yeon arrives first, reassuring Shin that Gun is handling the situation. Despite her presence being motivated by a desire to ease Gun's concerns, Shin cherishes the time they spend together, finding comfort in her presence. He confides in her, revealing that he resorted to self-harm as a teenager, a dark secret uncovered by Gun, who entrusted Han with his care. Shin fears that he inadvertently mentioned this in his emotional diary, prompting him to burn it in a fit of panic.
His frustration at Gun's seemingly endless loyalty to him resurfaces, recalling how Gun jeopardized his own health to save Shin at the bridge. Shin's gratitude towards Ju-yeon for helping him find a reason to live is palpable, and she encourages him to take things one step at a time, offering a glimmer of hope for his uncertain future.
Gun's arrival interrupts their moment, and as he witnesses them together, he withdraws, his expression unreadable. Ju-yeon, desperate to clear the air, attempts to explain, but Gun cuts her off, declaring his weariness with the complexities of their relationship and his desire to move on from his first love. Her attempts to stop him fall on deaf ears, and he labels her clingy, cruelly suggesting that this is the reason her father abandoned her. The slap that follows echoes through the air as Gun walks away, Shin watching helplessly from a distance.
Meanwhile, Han and Kim cling to the hope that the second trial will alleviate the side effects, but their optimism is shattered when Tae-oh triumphantly resets Mouse 109, threatening to expose the side effects to Gun if Han refuses to allow him to conduct the same trial on the latter. The stakes have never been higher, and the web of deceit and danger continues to tighten its grip.
Han discreetly imparts the news to Ju-yeon, who immediately panics, her heart racing as she endeavors to reach Gun before Tae-oh can lay claim to him. Shin, with a chivalrous heart, lends her a helping hand, and as they traverse the bustling cityscape, he offers a tender farewell, his gaze filled with warmth and understanding.
Meanwhile, Gun finds himself lost in a solitary jog, his mind a canvas painted with vivid memories of Ju-yeon. A call from Yeo interrupts his reverie, unveiling the truth that Tae-oh has made his way to the laboratory. Driven by a surge of urgency, Ju-yeon rushes to the hospital, her steps echoing her determination.
Upon arriving, she stumbles upon Gun, lost in thought at the tennis court, where echoes of Ju-yeon's gentle words resonate, urging him to embark on a fresh start. Frustration mingles with love as she chastises him for causing her undue worry, her tone laced with concern and affection. In a moment of tender intimacy, he silences her reprimand with a kiss, the scene from Bad-Memory Eraser Episode 13 etched in the hearts of all who witness it, a testament to their unyielding bond amidst the chaos.
