Because This Is My First Life (2017)

Both focuses on women 30+ finding love but the biggest similarity is the close female friendships and how they all experience different loves and relationship challenges.

Both showcase healthy relationships between the leads and deal with their emotions in a very subtle and sensitive manner. They are both rooted in reality and deal with prevalent issues without being preachy or boring. It's definitely refreshing to see male leads respecting their partners and giving them their space. They are both slow romances, Radiant office more so but that's part of what makes it so gratifying at the end. They are not your typical K dramas and are hence grossly underrated. They are not for everyone but they're definitely worth your time.

While the overall story lines of 20th Century Boy and Girl and Because This is My First Life are fairly different, the way the stories are presented are quite similar. They shows split the screen time between couples and occasionally pull them back together for shared scenes. Also both shows have a wholesome light feeling throughout!

Both “She and Her Perfect Husband” and “Because This Is My First Life” plot’s purpose is on contract marraige

Yae, an unremarkable girl working in a café and living with a friend, finds herself unable to afford rent when her friend suddenly gets married, and she loses her job in the same day! It’s only when her boyfriend dumps her that she finally hits rock bottom. She’s at her wits’ end when her childhood friend Takumi suddenly reappears into her life. Takumi suggests that Yae take on a part-time job as his “fake wife” for the next six months. He has his reasons for wanting people to think he’s married. Yae has no other choice but to accept his proposal, and in return receives housing and living expenses for playing the role of his “fake wife.” So begins a “fake marriage” with a time limit. Unbeknownst to Yae, she was Takumi’s first love, even though she thinks of him as nothing more than a childhood friend. Takumi struggles awkwardly but earnestly to win Yae’s heart and find true love. Even though their marriage starts as a sham, will the day come when this couple can become something more?

Same director, so it creates a similar feel. If you laugh while watching What’s Wrong With Secretary Kim, Because This Is My First Life will make you laugh.
Both male leads don’t believe in love, but end up falling in love.
Funny important person giving advice to the male lead.
Same sound effects.

Both dramas are very progressive and make a social commentary about the struggles women face in and outside the workplace. From sexual harassment to gender discrimination and everything in between. Both are dramas that will leave you thinking.

contract marriage, cold male lead, adorable couple! well dont worry about the chemistry, the chemi was lit

Beside both have same male lead, both drama also very heartwarming. And they have similar plot so far on the fact that there's circumstances that make the leads live in the same house.

Similar:
- ML had trouble with his family which he half resolves and lets go of
- FL is cheerful but not an airhead
- ML is considered expressionless
- Funny elements mixed in with more dramatic plot
- Relationship evolution and chemistry between couples

Difference:
- BTMFL is more slice of life, while DOBY has supernatural elements
- BTMFL shows life youth as office workers, while DOBY shows celeb life
- BTMFL focuses on meaning of love and marriage for a multi-cast while DOBY focuses on main couple's love story

BOTH
three best friends going through love and life, bickering and helping each other with their love lifes. Both dramas deal with contract relationships (each girl has a contract relationship in kuankaantong.) all the characters are quirky and entertaining

Both ML are cold at the beginning and then change. Both FL are sincere and direct, which is refreshing in dramaland.

the story of two people with feelings for each other and just having a contract to live together. And there is a cat....

the story revolves around realistic love story and problem that community face nowadays...
a really mature story that will we think about love and live in a different perspective...

A group of women supporting each other in friendship as they deal with life and romance problems. However, it's at the next level because its realistic relationship problems are in a more post-marriage setting. A good mix of fun comedic moments contrasted with serious heartbreaking moments because sometimes life happens that way. This isn't their first life, but it just might be their first happy ending.