Recomendações

Both dramas have cops going undercover to break a drug dealing operation.
Both agents have super fighting skills.
Both agents fall in love during their undercover work.
Both agents almost die trying to accomplish their mission.

Both dramas portray a cop who goes undercover to break a drug ring.
Both agents get help from other civilians to help them accomplish their task.
Both dramas have seemingly dirty cops who complicate their task.

Both dramas have Lin Yu Shen as the main lead.
He plays a police officer in both drams.
In Undercover he plays an undercover cop who has infiltrated the drug gang.
In Master, Wait a Moment, he plays a cop who mentors a rookie cop.
Lin Yu Shen demonstrates his super fighting skills in both dramas.

Both dramas are about keeping and discovering secrets.
Both dramas deal with crushes and relationships.
Both dramas deal with school life. All About Secrets deals with high school life, while My Unicorn Girl deals with university life.

Male lead tries to deal with his artistic best friend's death. Both productions have similar vibe, and the plot is introduced through the dead friend's drawings

Older woman, and a younger man...In Love and Fortune, FL is way older like in 30's while ML is in high school...in the other drama, age is no issue, just the FL not wanting the success of the ML coming from her so that ML can stand on his own and be proud of himself

Older successful woman, and a much younger man...In I Hear Your Voice, ML is still in high school while FL is a lawyer...In the other drama, ML is a subordinate at work, FL is the Boss at work

Older Successful Woman and a Younger less successful man...In Witch's Romance, FL gave the ML a chance till she discovered he is way younger...then deal's off...however, the heart speaks for itself...In Oshi no Oujisama, FL ignored her feelings for the ML for a reason...not age

Older Successful Woman and a Younger less successful man...In Find Yourself, FL was well aware she is inlove with ML but just kept him a secret because of societal pressure, in Oshi no Oujisama, FL never gave him a chance in the first place...until it affected her job and personal life....

Older Successful Woman and a Younger less successful man...In Encounter, they met on a holiday abroad coincidentally and in Oshi no Oujisama, met on the street coincidentally...In both dramas, they became Boss-Subordinate at work

Older Successful Woman, Younger less successful man living in FL's house...Same vibe, same feel...just less romantic excitement from Oshi no Oujisama

DGs plot summary somewhat made me remember about IOTL. in Both dramas leads butt head on a tv show, one lead was somewhat famous and the other was psychologist/psychiatrist .

* These two are Kim Seon Ho’s representative works
* Beautiful music
* Similar shooting/production technique
* Both are the growth story
* Both feature 'Halmeoni'
* Both may make you cry
* Both feature hand-written diaries/letters
* Poetic
* Remarkable golden words
* (More...)

In addition to the above, someone might treat Hometown Cha-Cha-Cha as Season#2 of Kim Seon Ho's story. There are many fan-made pictures of the 2 TV shows to relate Han Ji-pyeong and Hong Banjang's past. And this situation adds a lot of entertainment.

There are so many common features on the two TV shows:

1. Sweet scenes, lots of
2. Make you fall in love
3. There is no bad guy but just relaxing
4. Feel good and laughing
5. Fate
6. Both male leads have trauma in the past
7. Family and friendship
8. Stories of second leads are also sweet
9. Man leads are very charming
10. Super expensive sport cars (haha)
11. The clothing...
12. (more...)

There are also some minor differences:

1. The storylines of Secretary Kim are much simpler than Hometown Cha-Cha-Cha's.
2. One is in the big city and the other is in a small seaside village.
3. One is with the finance magnate and the other is not.
4. One may make you laugh and cry and the other will only make you laugh.

The FL goes into the story she is editing and falls in love with the ML of the story in that story. Like TRoTAR, Lost Romance's FL also changed the fate of the original character. And that's where the fun begins :)