Yu-mi is pleasantly surprised by her new relationship and she gains a new perspective on love.

Yu-mi and Woong meet again during second-hand market meet up. Unlike Woong who thought it was a fateful meeting, Yu-mi is confused by what Woong said in the past as compared to his current situation. While Yu-mi is trying to enjoy her Christmas with Ba-bi, a message from Woong arrives.

After the breakup with Ba-bi, Yu-mi's writing improves greatly thanks to Writer Cell who has become the Prime cell. Now a successful entrepreneur, Woong is surprised to find that Yu-mi is now a writer. When he meets Control Z through a business meeting and learns that he is the illustrator for Yu-mi's works, his heart pounds restlessly...

A sudden confession leaves Yu-mi shocked, prompting her ‘Cell Village’ to activate its defenses as she suppresses her feelings.

As the war of nerves between Woong and Ba-bi rages on, Yu-mi is put in a tight spot by the unexpected three-way encounter... Meanwhile, Yu-mi finds out that Ba-bi is going to America for a business trip while planning for his birthday. With everything happening at bad timing, will getting back together with her ex be that hard?

At a friend's wedding announcement, Yumi mentions that she has a boyfriend. When her friends don't believe her, she proclaims that she will bring Woong to the wedding. But Woong is too busy, she has no choice but to... Just as she was about to give up, another situation crops up where it becomes necessary that Woong attends the wedding.

News of Ba-bi's date puts Yu-mi in despair. Yu-mi wishes he doesn't go on the date. But she couldn't tell him in the end... On the day of Ba-bi's date, Yu-mi falls asleep after feeling perturbed the entire day, when a message from Ba-bi arrives.

Although Yu-mi was taken aback by Ba-bi's sudden confession, her confidence level shoots up. Yu-mi becomes more preoccupied by Ba-bi and she unconsciously finds herself getting heated up when Ruby sets up a date for Ba-bi.

After being proposed to by Ba-bi, Yu-mi goes to meet Ba-bi's father. Yu-mi tries her best to make a good impression on Ba-bi's father, going as far as to summon her full-of-manners self. Meanwhile, Woong hears of Yu-mi's wedding and asks to meet her...

When Yu-mi hears that Ba-bi has returned to Seoul, she notes down the places that Ba-bi frequently visits to avoid him but ends up running into him at his go-to cafe. Having thought over countless times what he would say to Yu-mi if he meets her again, Ba-bi holds her back...

Yumi finally explodes in anger when Sae-yi moves houses. The breakup alarm gets activated in Yumi's cell village. They risk breaking up if Woong doesn't contact her in 24 hours. While the couple goes through a cold war, Sae-yi takes this opportunity to get between them.

Da-eun, an intern at Daehan Noodles' Jeju branch, likes Ba-bi but she decides to give up when she realizes Ba-bi has Yu-mi. Meanwhile, the chief editor at Julie Literature, Ahn Dae-yong, finds out that Yumi, the writer he picked, is his first love from his college days and believes that this is fate...

Unlike her courageous start, Yu-mi continues to taste failure from all her contests. Despite Writer Cell's efforts to keep her mind together by recalling wise sayings, Yu-mi feels dejected at her own lack of talent... At that moment, she receives an offer from Mr. Nam to reinstate her position at Daehan Noodles.

Yu-mi starts working with the oddball illustrator Control Z. Although she's on the verge of exploding when Control Z nitpicks at everything, she controls herself to stay professional. When Yu-mi flies to Jeju to spend the new year with Ba-bi, she finds out that Ba-bi is giving up his lease.

Cells live inside Yumi's head, a 32 year-old who works at Daehan Noodles' finance department. In her dull life where her main concerns are what to eat or wear, only one thing excites Yumi and her cells — Woo Gi from Sales! He's handsome, gentlemanly, and 5 years younger... Age doesn't matter if he's just a crush, right? Or she thought, but Woo Gi keeps hanging around her. Is this a green light?

As the two of them start living together suddenly, they learn about the sides of each other that they never knew existed. Both Yumi and her cells grow to like Woong even more. If Woong feels the same too, perhaps they can...

Yumi and Woong decide to take a break. Yumi now has to spend time alone when she used to spend it with Woong, so she seeks advice from Ba-bi... After some time, the two of them meet again at the place they first met. What would Yumi's decision be? And what would Woong's decision be?

Yumi's Love cell is good at everything, but she has one weakness. Thus, the cells suggest that Ruby becomes her private tutor to help Love Cell! Meanwhile, Ba-bi who has been paying attention to Yumi's social media posts, gives Yumi an unexpected suggestion, making her heart race.

On the day of the wedding, Yu-mi is unable to meet the deadline. She falls into a panic when she loses her laptop containing the manuscript. At the wedding, all she can think of is running away from reality... At that moment, someone contacts Yu-mi and says that he found her laptop. Who could it be?

After Yumi brought up the topic of marriage, their relationship grows awkward for some reason. Meanwhile, Woong and Ba-bi attend the same dinner party by coincidence, and drunk Woong forgets everything that happened that night. What could have happened the night before? Woong feels anxious all of a sudden...

Yumi gets to go to the flower festival with Woo Gi, alone! However, Ruby keeps following them and disrupts the date of her dreams before it even begins. The ultimate chase between Yumi and Ruby begins. Meanwhile, Woo Gi makes up his mind to ask Yumi the question that has been on his mind.

Yu-mi's sweet romance with Ba-bi begins... Her new romance leads her onto a new path. When Yu-mi goes to a book cafe with Ba-bi, she is reminded of her long-lost dream. Although she knows it's too late, someone keeps encouraging Yu-mi to pursue her dream.