Resident Playbook Episode 12 opens with the residents discovering I-yeong and Do-won’s secret relationship. Though they promise to keep it under wraps, it turns out everyone in the hospital already knows. Do-won is later caught opening a new bank account, sparking wedding jokes from his fellow residents. His bashful “yes” only fuels their teasing.

Elsewhere, Jae-il continues to stay overnight at the hospital to support a cancer patient enduring excruciating pain. After researching relentlessly, he finds a combination of medications that finally gives her relief. His professor, recognizing his dedication, rewards him with a co-authorship on a paper—listing Jae-il as the first author.

Meanwhile, Sa-bi shadows Professor Ryu as they care for a patient facing surgery. Sa-bi, who has always struggled with showing emotion, is surprised to catch Ryu joking with the anxious patient. After surgery, Ryu repeats the same jokes, explaining that it’s his way of helping patients relax. Inspired, Sa-bi awkwardly tries her own joke in a sweet attempt to connect.

Over in OB-GYN, I-yeong and Dr. Seo handle a hectic New Year’s Eve as several pregnant women are admitted. Two younger mothers hope to give birth at exactly midnight to join the trend, but end up delivering earlier. One older mother delivers precisely at midnight, and I-yeong is given the chance to remove the placenta—a task she handles perfectly.

Nam-kyung, in another part of the hospital, faces a sobering moment as she loses her first cancer patient. Just as grief hits, Dr. Yang Seok-hyung rushes in with a mother in labor. Nam-kyung assists with the birth, experiencing the dual emotions of death and life within minutes—leaving her deeply moved.

Later, during a New Year’s meal with the residents, I-yeong shocks everyone by revealing she once won the lottery and had planned to quit the hospital. No one believes her—until she shows them the actual ticket. Then comes the heartbreak: the claim period has expired. She’s devastated by the missed chance.

That night, Do-won surprises I-yeong with flowers and matching couple rings, leading to a tender kiss. Meanwhile, Jae-il confesses his feelings to Sa-bi, who says she misses him but isn’t ready to date yet. They walk off together as he gently tries to persuade her.

Elsewhere, Gi-on officially joins the OB-GYN department and hints at his growing feelings for Nam-kyung. The next day brings big news—Dr. Chu Min-ha is appointed as the new OB-GYN professor over Dr. Myung. While everyone congratulates Min-ha, Dr. Myung swallows his pride and accepts the change.

Ju-yeong and her husband face another failed attempt at conceiving, and this time Ju-yeong decides to stop trying. Ironically, despite seeing Do-won and I-yeong holding hands, the couple remains blissfully unaware of their relationship.

In the episode’s final moments, I-yeong officially returns to the hospital as a second-year resident. Resident Playbook closes its season on a heartfelt note, embracing the rhythm of hospital life—filled with small joys, quiet heartbreaks, and subtle growth. Just like its predecessor Hospital Playlist, it delivers warmth, realism, and emotional depth.