Can someone suggest me a Jdrama with action plot or mystery or detective work as its main plot ans romance as its sub plot???

If you've seen/read the anime/manga Detective Conan, the live action is pretty good imo. I'd also suggest Erased which (also is based on a manga/anime and) has quite a bit of a mystery theme. 

 Origamy:

If you've seen/read the anime/manga Detective Conan, the live action is pretty good imo. I'd also suggest Erased which (also is based on a manga/anime and) has quite a bit of a mystery theme. 

I have seen the anime...grew up watching it actually....I’ll look into it !! Thank youuuu

Boku no Yabai Tsuma- This has everything you asked for mystery, detective, and romance all together

 ShotaSidePart:

Boku no Yabai Tsuma- This has everything you asked for mystery, detective, and romance all together

Adding it to my list!thank you 

Ice World. It's oldie but goodie :D

 kura2ninja:

Ice World. It's oldie but goodie :D

Agree with this one!

A funny one is Bitter Blood, has a wee bit of romance.

 kura2ninja:

Ice World. It's oldie but goodie :D

The summary sounds good....illl look into it...thank youuu

 kitty10:

Agree with this one!

A funny one is Bitter Blood, has a wee bit of romance. 

I’ve seen bitter blood.... it’s awesome!!!

 rdturbo:

Siren

Ohh this  is really close to what I am looking for.....thank you

  • Maou
  • Aishitetatte himitsu wa aru
  • Byakuyakou
  • Ouroboros

hyakumanen no onnatachi / one million yen women - early eps are really slow youd be left wondering where the heck is it heading, around ep 7-10  it gave me a shiver, it at least gave you somewhat a nice ending

byakuyako - tragic romance

Maybe you can try Mr. Brain, not much romance but it's guest are star-studded and it is very good.