Because This Is My First Life (2017)

Both drama's explore the personal struggles of adulthood. They both give an insight on the struggles of a woman against society and the perception on how they should be living their lives. Both main female characters live together with the male main character as well as focusing on other supporting characters that have their own struggles.

These dramas have a similar overall pace. They start with certain events that work as catalysts for the main plot focus, they have significant character developments and they explore questions that relate to love, family/friendships/work/romantic relationships, while characters are still learning about themselves.
The couples have amazing chemistry too!

1. Cold aloof male lead and cute female lead
2. Male lead had a previous relationship.
3. The female lead likes the male lead first.
4. Male lead is 7-8 years older than female lead.

Arrogant difficult nerds whom have been hurt with love, but find a new romance that brighten their lives.

Both have arregent hard to deal with nerds who have been hurt with love, but find romance in the most unexpected ways.

both main leads werent exactly on friendly term when they first met

have multiple couple, weird how exactly there were three couples

but what most similar between both drama is how through those ordinary characters they tackles real life everyday issues and explore human relationship in such an interesting way, though the plot and may seems cliche sometime but they have their own very twist that will leave you grinning by yourself.

both drama also revolve around marriage (not just dating as how most drama are) issue and how society view them

tho both ROMANCE COMEDY genre but actually they have a much deeper story than your usual romcom

another trivial similarity : both male leads failed their first marriage, main leads somehow end up living under the same roof.

Both Dramas deals about Marriage and Relationships, Divorce, Close Friendship, Second Lead couples and delivers relationship hardships and comedic slice of life story.

Falling in love after getting married! Goong has a bit more tears and teenage drama while Because this is my first life is a bit more mature but innocent in a way as well, both are focusing mainly on the development of the main couple's relationship. Also, the main actresses look quite similar.

I recommend this both drama because , Male lead and Female lead
try to solve problem
In one drama explosion and another student murder/suicide

Both dramas are sweet and about two totally different people developing feelings for each other as they learn to depend on the other while living together, although Kimi wa petto is a bit more extreme with the conditions for tenancy ;)

Both deals with relationships, family problems and friendship. They have similar vibe and you can easily understand characters because they have problems like we, ordinary people have. Also I feel like they are both healing dramas, if you know what i mean:-).

To put it simply the similarity is in

the love after marriage genre

A seemingly odd couple composed of a cold male executive who pairs with a younger female and the relationship that slowly builds between. Both dramas start with fake relationships that develop into cute romance.

The similarity lies in the
Very simple cute leads
working busy male lead
The love after marriage genre

They both same the same vibe
The main female lead s the same as the supporting lead there and have similar personalities