Recommendations

Both have the opposite attracts romantic comedy mixed with a bit of a catch-the-cultprit/murder-mistery.
While the genders in both hero and heroine are reversed they involve one main lead, which is calm, seemingly mature and well-educated person and another one, which is loud and lacks basic culture. Surprisingly they both make great couples.
Both leads (genders reversed) are surprisingly successful in their work even though their lack of education and do it from a long time so that they help their family.

The overall atmosphere of these dramas are very different, but in terms of friendship, both of these dramas feature a sisterhood that I really long in a drama. In Be Melodramatic, they have been friends for a long time already and have been living together. Meanwhile in the The One and Only, they are living together in a room not by choice but by circumstances, but are already united by one secret. I really like these sets of friendship because of how different their personalities with each other.

Both start off with two people with totally different believes, lifestyles and overal world views. After their strange first meeting in which the male lead takes a notices of the female lead (and he seems to be the first one quite smitten with her) the main leads start interacting at their workplace.
Both main leads start living together (in the same building, but different floors) and due to their communication solve all of their problems.
Both dramas have good communication between the mains (mainly, but not only throught conversations).

Having mentioned this by a couple of users in the comment section, I agree that they are similar in certain ways. Even though The One and Only just have released 2 episodes, I can already similarities in the main couple. They are both scarred by their traumatic childhood that heavily influenced their present lives. In JBL, it seems that the main leads are positively influenced by their childhood (like how they chose their career) but I can not say the same for the couple in The One and Only.

In both drama you will find communication between the main couple. They actually sit down and talk things out(well most of the time) bubbly/cold theme where the ml falls first, and of course there is a dash of a past love interest popping up along with the issue that arises in the last 5 episodes.

f4 (+ previous versions) and moon lovers are my favorite dramas by far. moon lovers is truly a masterpiece, and actually very similar to f4 in my opinion:
- FL is courageous, strong, kind, funny, and stands up to the ML. she really is the ML's ray of light.
- ML is kind of an anti-hero. his mom is VERY similar to thyme's mom, and grew up in a very cold/abusive environment. this causes him to be violent, impulsive, and everyone is scared of him. when he meets the FL his world becomes bright, and he falls heads over heals first. like in f4, the FL is in love with someone else first. the ML kind of bullies/teases the FL before professing his love (that scene still gives me chills)
- ML is persistent, says he'll never let her go, etc.
- there is a reverse-harem-- a bunch of good looking guys who are praised (bc they're the sons of the king)
- overall, the plot is so interesting! the FL travels back to the Goryeo era in ancient Korea. it made me cry so many times, and is by far my favorite drama other than f4/BOF <3.

Similar plot & storyline. I recommend this drama if you like fantasy genre drama. I really enjoy this genre.

A taboo relationship. Ireland is more to brother & sister love. I enjoyed this kind of genre coz of unique storyline & different plot from other drama. Is not a everyday drama/movie that you can watch easily. This genre is recommended if you like a different kind of plot & worth watching.

I watched this drama coz of the cast. Similar love affairs in marriage. Not confusing plot & easy to understand. The FL feeling lack of love & care to her husband after many years of marriage. She feel her husband is more like a buddy than partner. If you like this genre I recommend this drama.

This drama is not really focus on love affairs. The ML & FL tried their best to protect their marriage. Both of them got a fling outside but only for a really short time. If you like love affairs drama with light plot I recommend this drama, only 23 minutes per episode.

Continuation from Hirugao Japanese drama 2014.
Love affairs between Sawa & Yuichi. I recommend both drama & movie. Saito Takumi is too adorable & cute!

Compare to this drama is very heavy with intriguing plot. Both FL & ML tried to protect their marriage by keeping a secret from their partners & they set a rules together to deleted message from each other & no calling if not urgent. Saito Takumi is soooo hot & good looking. If you like this genre I recommend this drama.

Compare to Anata no Koto wa Sore Hodo this drama is very heavy with intriguing plot. Both FL & ML tried to protect their marriage by keeping a secret from their partners & they set a rules together to deleted message from each other & no calling if not urgent. Saito Takumi is soooo hot & good looking. If you like this genre I recommend this drama

Continuation of Hirugao drama 2014, secret love affairs between Sawa & Yuichi.
Compare to Soredemo Ai wo Chikaimasu ka this drama is very heavy with intriguing plot. Both FL & ML tried to protect their marriage by keeping a secret from their partners & they set a rules together to deleted message from each other & no calling if not urgent. Saito Takumi is soooo hot & good looking. If you like this genre I recommend this drama.

Compare to Soredemo Ai wo Chikaimasu ka this drama is very heavy with intriguing plot. Both FL & ML tried to protect their marriage by keeping a secret from their partners & they set a rules together to deleted message from each other & no calling if not urgent. Saito Takumi is soooo hot & good looking. If you like this genre I recommend this drama.