Episode 10 of "Family By Choice" kicks off with Joo-won feeling distinctly uneasy about the homecoming celebration that involves Hae-joon and San-ha. She repeats, with a hint of firmness, that they do not constitute a conventional family and informs the group that she has prior engagements on her birthday, making her unable to join them for dinner.
Returning to her shared apartment with Dal later, Joo-won fills her in on Hae-joon and San-ha's unexpected appearance. The next morning, as they step out, the two friends stumble upon their new neighbors—who happen to be Hae-joon and San-ha! San-ha swiftly shifts the blame onto Hae-joon, leaving him to clarify the situation to Joo-won. It becomes evident that the duo deliberately rented the apartment adjacent to hers. Joo-won invites San-ha to visit her bakery for a chat. While Hae-joon is there, she hands him her card to purchase new sneakers, noting his shabby attire.
San-ha embarks on his new job at a nearby hospital, where he is joined by Lee Joon-ho and Do Hui-ju, both practicing doctors. Meanwhile, everyone assumes Hae-joon is jobless, prompting the dads to scrutinize their savings account to assist the "kids." In reality, Hae-joon has been scouting locations in the city for Jung-jae's new restaurant.
As San-ha walks Joo-won back home, he wishes her a happy birthday before rushing back to the hospital. Unbeknownst to him, his mother and sister believe he's simply on vacation.
On Joo-won's birthday, the family eagerly waits for her at breakfast. Just when it seems she might not appear, Joo-won silently takes her seat, hinting at a possible softening in her stance. Post-breakfast, she reproaches Hae-joon for cutting ties with them for over five years. Hae-joon remains silent, unable to respond, until San-ha comes to his defense, revealing that Hae-joon had suffered a severe leg injury, so grave that the doctor feared he might never walk again. Hae-joon kept this from everyone, and the revelation brings Jung-jae to tears as he blames himself for letting Hae-joon go. The three "kids" excuse themselves, leaving the dads some private time to process the news.Later on, Joo-won inquiries about San-ha's prolonged absence over the years, uncovering the truth that his mother had forbidden him from leaving, despite San-ha's deceptive claim of mere busyness. In the meantime, Hae-joon and Jung-jae mend their fences. As dusk falls, Joo-won, Dal, and the two boys arrange a gathering to mark Joo-won's birthday, but unexpectedly, the news leaks out due to Hae-joon's slips of the tongue, leading to an unexpected turnout. When the celebration winds down, San-ha fails to arrive punctually, instead leaving Joo-won's gift hanging on her doorknob.
The following day, Joo-won expresses gratitude to San-ha for the thoughtful present but politely declines his invitation to meet up. Subsequently, Lee Jun-ho casually mentions Joo-won's plans for a date that evening, which disturbed San-ha's peace of mind. Meanwhile, Dal cleverly persuades Hae-joon to treat her to hangover soup.
That very evening, San-ha makes his appearance at the bakery but struggles to reach Joo-won. Fortunately, fate intervenes as she returns to fetch her phone, presenting San-ha with the opportune moment he's been waiting for. After a decade-long silence, he finally opens his heart and confesses his deep-seated feelings for her.
