Recommendations

FL leads have their own charming point
Cold ML who keeps helping FL like an under cover
Youth and College life
Friendship

They both same because :-

-the ML is an idol
-the FL is ML 's assistant
-they fall in love with each other

Both are historical dramas
Both have FL and ML that surprise you with their actions
If you liked one you will probably enjoy the other

Both are historical dramas
Both are about a lost/abandoned princess
Both are tragic stories
Both Female Leads are princesses that suffer while trying to find their identity

Both dramas have a "perfect" ML and "mediocre" FL falling in love. Also the ML in both dramas is helping the FL with her studies and they are cohabiting.
In P&C they are both adults and start with a student-professor relationship while in InK they are in high school to university. There is also no contract marriage in Itazura.
I enjoyed both.

If you like Thai drama Nakark Kaew, then you may enjoy the South Korean drama Birth of a Beauty.
Both dramas has a plastic surgery storyline .

Both dramas deal with the pain of loss and emotional struggles. Both have such a sweet but gradual love story. Both are so pleasing to watch. Both have an overpass that holds significant meaning. Both have wonderful supporting casts that support the main characters.

Both Be Melodramatic and Into the Ring are funny, unique and have a slower pace. The differences I would say is that Be Melodramatic deals with more serious and heavy stuff at times that Into the Ring does not. Overall the best thing I could say is they have the exact same vibe and at times the same music.

The themes are different, but both of these shows are the same quality level, and that's not a compliment, lol. Both have a late-night trashy vibe with a story that requires you to check your intelligence at the door. The MLs in both are hair-pullingly frustrating.

If you want the more watchable version of this theme (woman hired to have a child by a rich family), the try Leh Ratree. So Sanaeha has the same theme but is a more frustrating watch. The two FLs are also night and day (sarcastic and bitter vs innocent in Leh Ratree). But the MLs kinda act the same toward the FL, in the beginning at least. The MLs even have a similar look.

Similar in
- themwork
- great cemistry ML - FL
- tint of humor to dramatic stories
- similar ML - stoic, righteous etc
- similar FL - thirst for justice, bold, and full of spirit, takes matters into own hands
- tragic backstories
- detective work

Similar in
- Detective work
- Psychological sub theme
- both FL have strong justice spirit
Difference
- one is has a more grim atmosphere while the other is also comedy

Cold ML in white suffering from lifelong disease is always keeping an eye and coming to the rescue to the fiery badass FL who misunderstands him. He is also key in her martial art training and turns her into a weapon that can possibly turn against him. Lots of duels between ML and FL and sexual tension.

Similar in atmosphere story and chemistry.
About the relationship, both are incompatible entities that work together to save people and solve mysteries.
Wonderful teamwork.
Both are horror comedies.

Both dramas include supernatural elements and revolve around a private investigator and his assistant