My favourite kind of male lead!
+ 1 Love & Destiny - Chang Chen is really gorgeous in this & he's perfect as the God of War. The way he singlemindedly focused on protecting/saving his Queen was so heart fluttering. :)
+ 1 Padam Padam - Jung Woo Sung is amazing in this role! And effortlessly gorgeous even when he's playing a gruff, down on his luck ex-convict.
Prison Playbook - this drama is not purely centred on romance, but trust me it's there! The fact that romance isn't listed as a genre is very misleading & one of the reasons why I ended up not watching the drama for a long time because I thought it was mainly focused on sports. The male is a pro ball player who is in essence a very simple guy (sometimes he may even come across as simple minded, but don't worry, he isn't). He just has a very one track mind, can only think/focus on one thing at a time ... I guess like most men. Anyway, he was a pretty unique male lead to me ... in the sense that while he was very good at baseball, he wasn't that 'smart' otherwise, like most other MLs who are bordering on being geniuses. His relationship with the female lead was really cute.
Cruel Romance - trust me the romance is far from cruel & the ML here is so dreamy, he's every woman's fantasy man!
Aishiteru to Ittekure - old but super gold and sooo romantic. The ending is not the most elegant, but the journey is worth it!
The Masked Lover - this one has crime/action & lots of romance! In fact, you get 2-for-1 bonus because the 2nd leads romance was quite heart catching, although I found the 2FL just a tad bit annoying. Anyway, worth the watch!
Others
Can We Love?
City Hall
The Greatest Love
Second To Last Love* - haven't seen this one personally, but I know ML fits what you're looking for.
Honourable Mention
Hope All Is Well With Us - this is not romance focused, but relationship focused. There's a lot of chemistry between the ML and the FL, but they never quite got together in the drama itself ... well, because the ML was really devastated by his divorce and couldn't focus on any new relationship right now. He needed to heal his heart first and get back on his feet, which is what the drama focuses on, but the FL is present, she supports him & helps him out when he needs it most ... they just never really went the romance route. I think this drama is really worth the watch, though, if you like dramas about family and second chances. Plus the ML's little son is sooo adorable & their time together as father & son is precious. I definitely recommend you give it a go ... and if that's not incentive enough for you, just know that the ML is fine AF in that gruff, rugged manly sort of way!!! lol