Episode 9 of "The Potato Lab" unfolds six years into the past, where Mi-kyung stands eagerly at the airport, awaiting Ki-se's return from a business trip. Ong-ju and Hwan-kyung accompany her, laden with festive food meant to celebrate his homecoming. However, Ki-se fails to materialize, informing Mi-kyung via a cold message that he's caught up with work colleagues, effectively ditching her.
At the workplace, Ki-se's demeanor towards Mi-kyung grows increasingly frosty, warning her to exercise restraint in physical closeness. Soon after, he proudly displays his wedding invitation to Hee-jin, an announcement that Mi-kyung refuses to accept but which nonetheless shatters her heart into pieces.
Flash forward to the present, where Mi-kyung finally connects the dots and identifies Hee-jin. She interrupts Baek-ho's explanation abruptly, seeking fresh air outside. Baek-ho, ever the attentive companion, follows suit, offering her a comforting cup of coffee and reassuring her of his unwavering support. Touched, Mi-kyung bestows upon him a sweet peck on the cheek.
Downstairs, Ki-se confronts Hee-jin, his patience worn thin by her pretense of normalcy. He lambasts her for vanishing overnight and leaving him to search for her in vain for years. While he no longer harbors resentment, he claims she mistreated him during their marriage.
Hee-jin counters that he never truly invested in their union, asserting that she clung to the fading threads of their love until she reached her breaking point. The elephant in the room, of course, is Mi-kyung. Hee-jin eventually exits the conversation, wishing him a life of perpetual misery.
Elsewhere, Baek-ho takes Mi-kyung on a date to indulge in ramyeon, only to find himself slipping back into work mode, eager to tidy up their surroundings. The humor in the situation is not lost on onlookers. Ironically, they bump into Hee-jin just down the street, drowning her sorrows.
She soon joins their company, and Mi-kyung's mood darkens as she listens to Hee-jin reminisce fondly about her time with Ki-se, describing their romance as nothing short of magical. Hee-jin reveals that she initially visited the training program to see Baek-ho but ended up meeting "some attractive guy" – none other than Ki-se.
Hee-jin continues her narrative, unveiling a tale of love at first sight that rips at Mi-kyung's heartstrings as she absorbs every intimate detail of their shared moments. Overwhelmed by emotion, Mi-kyung excuses herself, informing Baek-ho that she'll meet him bright-eyed and bushy-tailed at the lab the next morning.
Upon arriving at the lab, the whimsical scene unfolds where workers converse through a blend of sign language and quirky little gestures, adding a dash of humor to the setting. The focus shifts to Seung-hoon, who's ensconced in his own booth, steadfastly refusing to budge from the lab. His stubborn stance stems from his role as Section Chief—he's determined not to be the first to leave, clinging to his pride. Eventually, his resolve melts away, and he succumbs to tears, calling out to his mother as if the heavens themselves could answer.
Mi-kyung returns home to a startling revelation: On-gju has vanished, unable to bear the pain of hurting their friendship by staying close. She's ended things with Hwan-kyung and fled, her love for Mi-kyung too profound to endure the heartache. Unbeknownst to Mi-kyung, On-gju had been her brother's first love, his affections never wavering. When Mi-kyung comprehends the gravity of the situation, she's left reeling and sets out to mend what's been shattered.
Baek-ho lends his support, and eventually, they're all reunited, their differences bridged. To solidify their bond, they establish a few house rules, ensuring harmony and understanding reign supreme.
In the meantime, Ki-se finds himself lost in nostalgia, reminiscing about the joyous moments he shared with Hee-jin. Determined to clear the air, he confronts Mi-kyung with his thoughts. He confesses that Hee-jin is unaware of Mi-kyung's existence and has been visiting the Guesthouse solely out of concern that Mi-kyung might make a spectacle, revisiting their shared past. Ki-se further elaborates that Hee-jin abruptly disappeared from his life, ghosting him and even divorcing her previous partner before taking refuge at the Guesthouse. Post her disappearance, she settled all matters through a lawyer, avoiding all his calls and messages, leaving him without a chance to confront her. The reasoning behind her actions remains a mystery, unknown even to those at Wonhan, as Ki-se had kept the entire situation under wraps.
It's evident that Ki-se is terrified of embarking on a new journey and breaking free from his current funk, prioritizing the title of Executive Director over his own happiness and life's direction. Though Mi-kyung admits that seeing him miserable and struggling brings her a twisted sense of satisfaction, she eventually offers him words of wisdom, urging him to strive for something meaningful in his life instead of dwelling on past mistakes.
Elsewhere, chaos unfolds in the lab as the group discovers that all the greenhouse doors have been left ajar. Seung-hoon casually admits to being the culprit, brushing it off as if it were nothing. When Mi-kyung learns of this, her anger boils over as she explains the importance of keeping the doors closed. Unfazed, Seung-hoon dismissively remarks, "They're just potatoes," further irritating everyone.
Hee-dong, one of the women, grabs a metal bat and chases Seung-hoon out into the parking lot! However, it's Mi-kyung who has the final laugh, threatening him at work knowing she's soon to leave the company and has nothing left to lose.
After patching things up with Seung-ho, Baek-ho takes Mi-kyung out for the afternoon. During their outing, Mi-kyung revisits the incident that occurred six years ago, revealing how it had toughened her up.
When Mi-kyung embarked on her journey at the potato laboratory, she demonstrated remarkable perseverance through the toughest of times, enduring even the unseasonable, terrifying snowfalls that blanketed the land in the unexpected chill of May. Under such grueling circumstances, many might have thrown in the towel, but not Mi-kyung. She exhibited an unyielding spirit, pushing forward against all odds.
Amidst the blizzard's fury, she stumbled upon a "miracle potato" – a solitary plant that had somehow withstood the brutal cold and the impenetrable darkness. This resilient potato became a beacon of hope for her, igniting within her a renewed determination to live and discover a fresh purpose in her existence. And indeed, she has embraced this newfound resolve, relentlessly pursuing the creation of a similarly resilient potato variety.
Elsewhere, Baek-ho found his words, sort of, in the form of a tender kiss that sealed their moment with unparalleled romance. As Mi-kyung made her way home, Ong-ju eagerly awaited, insistent on hearing every last detail.
Hee-jin awoke to the sorrowful news of Ki-se's father's passing. This man, who had always placed Hee-jin's family above his own, now haunted her thoughts with his selflessness. Though heartbroken, Hee-jin attended the funeral with warmth towards Ki-se's mother, offering her condolences before departing swiftly, yet encouraging Ki-se to reach out if he needed anything.
Here, the truth about Ki-se and Hee-jin's relationship came to light, unraveling the fabricated image Ki-se had painted earlier. The drunken declaration of their perfect union? A mere illusion fueled by lust. Their marriage had devoured their love, evident in Ki-se's forgetfulness of Hee-jin's birthday and shoe size, culminating in his alcoholic escapades. Ki-se's depression and resentment over his life choices alienated Hee-jin, despite her efforts to reconnect. His bitterness towards the world was too consuming.
Outside, Mi-kyung arrived, and with tears streaming down his face, Ki-se confessed his regret for their past and his hasty escape into Hee-jin's arms. As he sobbed on her shoulder, Baek-ho appeared on the scene, quickly realizing that she was, in fact, Ki-se's ex.
