In the opening scene of Episode 1 of Yumi's Cells Season 3, Yumi's father, Kim Man-sik, proudly boasts to his neighbors about his daughter's success as a romance novel writer. She has bought him a new car and even had one of her novels turned into a drama. He gives Yumi a call, and we learn that she is going skydiving with her producer, PD Yoon. She's doing research for her new book, which involves a character falling in love with her skydiving instructor. As she and her instructor jump out of the plane, Writer Cell realizes that she needs a different setup for the story.
Elsewhere, Yi-da and Dae-yong, who now have a baby girl, head out of the house. Yi-da visits Yumi at her new studio, where they discuss how Yumi hasn't been able to write lately despite already having four hits. Yumi says it's because her life doesn't have any problems and that she's bored. But Reason Cell tells us that the real reason is that Yumi's cells have started disappearing as the Writer Cell became more powerful. Even Love Cell has disappeared after claiming to be bored, since Yumi hasn't dated anyone for three years.
Reason and Emotion Cell look for the missing cells and end up finding a massive freezer with all the dormant cells that Yumi doesn't use anymore. On the outside, Yumi admits that she likes the lack of emotional ups and downs. After Yi-da leaves, Yumi gets a call from Dae-yong, who tells her that PD Yoon has injured his leg from skydiving. So he will be assigning a new PD to her. Someone who is calm and rational and won't suggest jumping out of a plane.
In Yumi's head, Emotion Cell starts to feel sleepy as well, and Reason Cell carries her out of the freezer. At Yumi's place, the new PD, Shin Soon-rok, arrives and is welcomed by Yumi and her assistant writer Baek Na-hui. After Na-hui leaves, Yumi realizes that Soon-rok used to work at the company before as well and had met her three years ago. He left for a bit and has now returned to this company. However, his behavior is straightforward and calm to the point of being cold.
As Yumi exits her studio, she unexpectedly finds herself sharing a bus with Soon-rok, a fellow resident of her neighborhood. Despite Manners Cell's strict guidelines prohibiting her from donning her earphones, she's taken aback when Soon-rok effortlessly breaks the rule with his own. Their chance encounter comes to an end when they disembark, but fate has other plans. Yumi encounters him once again at a bungeoppang store, where he arrives first and secures the last remaining servings, leaving Yumi with none despite her subtle hints.
That night, the Dislike Cell comes to life due to Yumi's strong dislike for Soon-rok. Additionally, we learn that Yumi has become a regular dog sitter for Ruby's Maltese pooch, Coco. The following day, Soon-rok's presence at Yumi's while Coco is still there adds fuel to the fire, with his one-word answers further frustrating her. They're soon joined by Na-hui and PD Jang, another producer.
During their work session, Soon-rok suggests Yumi change the breed of the dog in her story from a Maltese to something else, arguing that the breed isn't known for its intelligence. Yumi counters with fabricated statistics to defend the intelligence of Malteses, and Soon-rok drops the matter. Later, he calls to inquire if he left any documents behind and mentions the dog competition she cited, informing her that Malteses are notorious for eating their own poop. The episode concludes with Yumi exclaiming a curse word, awakening the Profanity Cell!
