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 when her roommate and younger brother wants his pregnant girlfriend to move in. Meanwhile, Se Hee is looking for a new housemate.

After a first kiss with a stranger, Ji-ho learns he's her landlord; homeless again, she and Se-hui regret they can't live together due to gender.

When Ji Ho gets a proposal from 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 marry, leading Ji Ho to introduce Se Hee to her family; Se Hee seeks Ji Ho's father's approval while Won Seok attempts to reconcile with Ho Rang by buying her a desired sofa.

Ji Ho and Se Hee's parents meet for the first time, disagreeing with the couple's decision to forgo a wedding; Won Seok remains confused about the reason for Ho Rang's anger.

Ji Ho feels closer to Se Hee after their wedding, while Won Seok and Ho Rang encounter each other at the event; Sang Goo confronts Soo Ji's mistreatment, expressing his disapproval.

Bok Nam helps Ji Ho get a job at the cafe. 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. Meanwhile, Ho Rang comes up with a plan to make Won Seok 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.

Ji-ho develops feelings for Se-hee, enjoying their daily interactions; Se-hee's mother's surprise visit disrupts their routine, while Sang-goo struggles to resist Soo-ji.

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 her colleagues at work made a bet about her, she becomes furious.

Ji-ho and Se-hee return home after their first kiss, bidding goodnight outside their bedrooms; Ji-ho experiences a strong desire for the first time in her life.

Soo-ji confronts Sang-goo for invading her privacy, while he attempts to understand her perspective; the friends learn about Won-seok and Ho-rang's breakup as Ji-ho receives a job offer from a production company.

Se-hee encounters Jung-min unexpectedly; when Ji-ho meets Jung-min the next day and inquires about her past, Se-hee realizes he has moved on from Jung-min and only worries about Ji-ho.

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?