Aquamaraqua:
Mainly looking for a hate to love drama with a MATURE male lead. Serious and sensible.
I'm trying to rack my brain, but your category has proven to be difficult to find, as far as Jdramas are concerned. The following dramas are not strictly "romance", but it does have leads that have some sort of mutual dislike towards each other (while maybe attracted to each other, subconsciously). All three have open ending, and their leads are generally well-adjusted adults, despite some personal quirks.
Bonus:
- Haken no Hinkaku (the dislike was entirely one way, and the guy who eventually fell in love with the heroine is kinda petty)
- Massugu na Otoko (it's not like the male lead hated the female lead, it's more like she has the kind of personality that drove him nuts; he always helped out whenever she's in trouble, though, right from the start)