Super obsessive and manupulative male lead...

Awww I love their plot soooooooooooooo much, wish there were more like that in Kdramas!

Most of the ones I know with crazy obsessions like that are second male leads and unfortunately there aren't that many of these either. Nothing has beaten his obsessiveness for me yet, but I enjoyed the ones below:

Beware possible spoilers ahead!

Subjectively depending who you consider male lead here, but Empress Ki has a very obsessive guy who would force the main girl to stay by his side at any cost. He is a cry baby and not a tough guy, but when it comes to female lead staying with him he is ruthless and I'd even say evil. Patience here as it's 51 episodes long and it takes a few episodes for him to fall in love.

The King's Woman (Chinese drama) - has an obsessive/possessive lead. I've only watched the first few episodes, but already he made sure the girl stays with him despite her being unwilling. 

If you haven't watched those already The Heirs, The Secret Garden, Noble my Love, My Secret Romance, Meteor Garden 1 (Taiwanese version of BOF) all have a bit of this, but in a less crazy way, the male leads are as insistent as a fly that found something smelly, go around and bother the main girl in the same way. 

Cheese in the Trap - very abnormal guy and certainly unhealthy/stalkerific attraction to the main girl, threatening people that could separate them in any way, very manipulative.

5-ji Kara 5-ji Made (Japanese drama) - a cute stalker like main lead that wants to marry the female lead no matter what.

I eagerly await more recommendations myself ;-)

Definitely you should watch: 

Summer's Desire

Lee Jun Kai

cdrama:  boss & me (title says it all)
love me if you dare ( a very picky criminal psychologist and his assistant)
love o2o (popular guy, he's quite and smart but is very detailed and is always aware and understanding of different circumstances) 

kdrama: heart to heart  ( main lead gradually starts liking her, a lot may I add)
high society: (mostly the second lead)
I have a lover ( ex husband realizes his mistake)
kill me heal me ( not exactly the lead)
moon lovers ( male  lead w/female lead, so many guys like her lol)
noble, my love  (rich guy, normal girl)
the greatest marriage ( mostly baby daddy, and a little bit of  coworker )

Bonus: Master devil do not kiss me (very rich guy trying to control and basically kidnaps the female lead)

All of these probably didn't take it as far as in my heart twinkle twinkle except master devil do not kiss me but I found that whole plot ridiculous and the quality of the drama isn't that great.  My favorites are in bold. hope this helps!

I second the person above me. Thai lakorns are a good place for that kind of story line. I would suggest U:Prince the Handsome Cowboy from Thailand (it is a lighter slap kiss kind of drama but it would prepare you for some of the crazier stuff.)
I also suggest Behind Your Smile from Taiwan. I really liked this one and finished it in like 3 days!

Princess Wei Young - Though it's the second male lead that becomes possessive. He becomes extremely obsessed with the female lead, and he's already this vindictive guy so he does about anything to get her. It's long, but it stays interesting with the politics woven in, and the female lead creates clever plans to stump her enemies. 

Have you tried General and I? The male lead forces the female lead to marry him and will do anything to keep her with him.

Thnks Tara and OldAnimelady for your rec....:)