Episode 6 of "Family By Choice" kicks off with Seo-hyun's return to confront Jung-jae, where she tenders payment for his nurturing of Hae-joon over the years. Jung-jae, taken aback, urges her to reunite with Hae-joon, who has eagerly awaited her for a decade. Seo-hyun, however, reluctantly declares that she cannot offer Hae-joon false aspirations of a shared future and insists on keeping their encounter a confidential matter. Jung-jae steadfastly declines the money, returning the envelope to her and only accepting back the loan he had previously extended. Left puzzled by Jung-jae's actions, Seo-hyun reluctantly hands the envelope back to him before departing.
Meanwhile, Hae-joon catches a glimpse of a figure resembling his mother exiting in a taxi, but dismisses it quickly as they ascend to the rooftop, finding San-ha dozing off while his clothes air-dried. Suddenly, San-ha receives a call from Jung-hee, alerting her that So-hee is missing. San-ha, joined by Joo-won and Hae-joon, sets out on an urgent quest to locate So-hee, who had sneakily taken her mother's purse to hail a cab and rush to see San-ha. So-hee ultimately finds herself at a restaurant in a neighboring village, prompting the owner to summon the police. Dae-wook, responding to the call, arrives to retrieve the lost child. San-ha, informing Dae-wook of her whereabouts, realizes with a start that the girl is Jung-hee's daughter.
He escorts So-hee to the noodle shop, where San-ha confronts her sternly for abandoning her home without alerting her mother. Jung-hee arrives on the scene, adding her voice to the reprimand, placing the blame on San-ha for So-hee's actions. Dae-wook steps in to defend San-ha, but Jung-hee insists emphatically that they are family, regardless of the circumstances. She urges San-ha to plea for forgiveness, highlighting her magnanimity in reuniting So-hee with him. San-ha, frustrated, snaps back at Jung-hee, pleading her to cease her futile attempts at mending their fractured bond.
The altercation escalates into a spat between Hae-joon and Jung-hee, triggering a panic attack in San-ha as haunting memories of his sister's demise resurface. Silently, he retreats to his home, skipping dinner and retiring to bed. That night, Hae-joon and Joo-won confer about the incident, and Hae-joon confesses a newfound understanding of San-ha's phrase "toxic family."
Over the subsequent week, Hae-joon and Joo-won take turns leaving breakfasts at San-ha's desk, despite his continued refusal to eat. A couple of days later, Hae-joon encounters San-ha at the bus stop and they walk home together. He gently advises San-ha that abstaining from meals isn't a healthy response to parental conflicts, sharing his own experience of having no parents to confide in, while San-ha still has Dae-wook as a confidant. Hae-joon assures San-ha that it's okay to feel embarrassed but important not to neglect meals.
The following day, Dal joins Joo-won as she delivers San-ha's breakfast to his classroom, revealing her intention to seek his assistance in calming her mother. San-ha returns to his class, his face lighting up upon discovering the note Joo-won left for him. He collects it, adding it to a collection of notes she's been writing him over the past few weeks, each one a testament to their growing connection.
On that fateful night, San-ha returned home later than usual, as the heavens opened up and a downpour ensued. Joo-won, worried, attempted to reach him by phone but, receiving no answer, braved the storm to search for him personally. San-ha, battling against the relentless rain, eventually made his way back, yet his body was weary and ill from the ordeal. Finding him drenched, Joo-won offered her umbrella and gently urged him to join their family dinner.
San-ha, seeking solitude in his turmoil, suggested it might be best if she left him to his thoughts. Ignoring his plea, Joo-won persisted, inviting him to share their meal. At the dining table, Hae-joon revealed that Joo-won had spent a full hour in the driving rain, her unwavering concern leading her to search tirelessly for San-ha. As San-ha took his first bite, the emotional weight of the day caused him to break down.
Later, atop the rooftop, the trio found solace in sharing their vulnerabilities, each revealing the person they missed dearly. San-ha, overcome by fever, lost consciousness, prompting Hae-joon and Joo-won to gently escort him to bed. Throughout the night, the family took shifts, keeping a watchful eye on San-ha’s condition.
The following morning, San-ha awoke to a renewed sense of well-being. Dae-wook, his father, took him to visit So-jeong's tombstone, where they reflected on how Jung-hee's words might have lingered in San-ha's heart for years. Dae-wook assured San-ha that So-jeong's passing was a result of their own inadequacies as parents, not his fault. San-ha, reassured, vowed to visit his sister's grave more frequently.
Life gradually resumed its normal rhythm, and the children prepared for school with lighter hearts. Yi-hyun, sharing the joy of his newborn daughter, sent Hae-joon a picture, inviting him to visit soon, his words filled with anticipation and warmth.
On their journey to school, Joo-won shares with his companions that Dal's mother has extended an invitation to a lavish meal. San-ha, a cynic of the world's transactions, remarks that such generosity often comes with hidden motives, suggesting that Dal's mother might seek something in return. Hae-joon, unperturbed, agrees to accompany them, while Joo-won reveals that Dal has a favor to ask.
At lunch, the trio joins Dal and her mother, but an uneasy atmosphere pervades as Mrs. Park publicly berates her daughter in front of her peers. Joo-won feels increasingly uncomfortable as Mrs. Park repeatedly labels Dal as ignorant for her lack of dining etiquette. She implores San-ha to assist Dal with her mathematics, and he attempts to assure Mrs. Park that with more practice, Dal's skills will flourish.
In a private moment, Dal confronts her mother, pleading for her to cease the insulting remarks as tears stream down her cheeks. Joo-won, noticing Dal's distress, feels a surge of empathy for her friend.
Post-meal, the children venture to the beach. Hae-joon, unable to mask his observations, comments on Dal's harsh mother, but San-ha quickly intervenes to shield Dal's feelings. While Joo-won and Hae-joon frolic in the waves, San-ha and Dal sit quietly by the shore. San-ha offers Dal his notes, praising her innate abilities and predicting a brilliant future as a lawyer.
San-ha gently advises Dal to view her mother as a flawed human being, which brings her a sense of relief. Hae-joon, sensing an opportunity, whispers to Joo-won that Dal might harbor feelings for San-ha, stirring a ripple of jealousy within her. Hae-joon's attention is then diverted by a call from Yi-hyun, prompting him to leave for his niece. Dal, too, departs for her academy, leaving San-ha and Joo-won to walk back home, their thoughts intertwined with the complexities of friendship and burgeoning emotions.
At the hospital, the nurse inadvertently discloses that Seo-hyun's presence is to reunite with Yi-hyun. Hae-joon is taken aback to discover that his mother has returned yet elected to keep her distance from him. That very evening, Jung-jae confides in Dae-wook about the envelope filled with cash, pondering over the best way to inform Hae-joon of this revelation. Hae-joon, catching sight of the envelope, collapses into despair. He's distressed by the fact that he's now unable to repay Jung-jae independently, given that Seo-hyun has already settled the debt.
Meanwhile, Joon-won edges precariously along the ledge, her hand securely held by San-ha. She remarks to him that Hae-joon is oblivious to Dal's affections for him. In response, San-ha playfully points out that Joon-won herself is not entirely perceptive. The episode concludes on a tense note as Joon-won, losing her footing on the ledge, tumbles onto San-ha.
