Because This Is My First Life

It's Ji Ho's 30th birthday and the worst day of her life at the same time. She becomes homeless overnight as her roommate younger brother wants her pregnant girlfriend to move in. Meanwhile, Se Hee is looking for a new housemate who can follow a certain set of rules.

The morning after Ji Ho kissed a total stranger, she wakes up to find out that her new housemate whom she thought was a woman is actually a man. Rather than the fact that they kissed, Ji Ho and Se Hee are sad that they can't live under the same roof as they are opposite genders.

When Ji Ho gets proposed by Se Hee, she becomes confused as she doesn't know what his intentions are. Sang Goo reunites with Soo Ji, but Soo Ji has no recollection of what happened before.

Se Hee and Ji Ho decide to get married, so naturally, Ji Ho introduces her boyfriend to her family. Se Hee must impress Ji Ho's patriarchal father in order to get his approval. Meanwhile, Won Seok tries to make up with Ho Rang by getting her the sofa she wanted.

Ji Ho and Se Hee's parents meet each other for the first time. Although Ji Ho and Se Hee agreed on not holding a wedding, Ji Ho's mom and Se Hee's dad think otherwise. Won Seok still can't understand why Ho Rang got mad.

After the wedding, Ji Ho feels like she and Se Hee have gotten closer. Won Seok and Ho Rang run into each other at the wedding. Meanwhile, Sang Goo gives Soo Ji a piece of his mind when he sees her being mistreated.

Bok Nam helps Ji Ho get a job at the café he works at. Even though Ji Ho tells him that she's married, he keeps coming onto her. When Se Hee sees the two together, he becomes jealous without even realizing. Meanwhile, Ho Rang comes up with a plan to make Won Seok a husband material.

When Se Hee learns about how Bok Nam got reported on the dating app, he looks into it with great interest without letting Ji Ho know. Sang Goo visits Soo Ji at a café near her office, but she acts cold towards him. Unaware of Bok Nam's intentions, Ji Ho agrees to drink beer with him.

Se Hee saves Ji Ho from Bok Nam. When the two get back home together, they have an honest talk. Ji Ho, Soo Ji, and Ho Rang go to a get-together between school friends.

Ji Ho starts developing feelings toward Se Hee and feels happiness from being able to see him every day. However, it does not last long as Se Hee's mother pays a surprise visit. Meanwhile, Sang Goo cannot resist Soo Ji.

Se Hee takes a day off from work for the first time and goes to Namhae in order to help Ji Ho's family with making kimchi. When Soo Ji finds out that his colleagues at work made a bet about her, she becomes furious. Before leaving to go see Se Hee, Ji Ho finds a poetry book that belongs to him.

After their first kiss, Ji Ho and Se Hee come back home and say goodnight in front of each other's bedrooms before going to sleep. For the first time in her life, Ji Ho feels a strong desire lurking inside her. Won Seok feels like something is off between him and Ho Rang. Meanwhile, Se Hee and Ji Ho go on their first date.

Soo Ji gets mad at Sang Goo for invading her privacy, and Sang Goo tries to understand her. The friends find out about how Won Seok broke up with Ho Rang. Meanwhile, Ji Ho gets a job offer from a production company.

Se Hee runs into Jung Min. When Ji Ho meets Jung Min the next day, she asks about her past. Se Hee comes to realize that he is only worried about Ji Ho and that he has gotten over Jung Min. Meanwhile, Soo Ji takes Sang Goo's advice and confronts his abusive colleague.

Se Hee accepts Ji Ho's suggestion to terminate the contract. Won Seok and Bo Mi go to a restaurant together and run into Ho Rang. Trying to ease the pain, Se Hee drinks until he passes out.

After Ji Ho moves out, Se Hee sells his house. Bo Mi tells Won Seok about her feelings and Soo Ji starts her own business. Will Se Hee and Ji Ho end up getting a divorce?