MARS is the drama that gives me most butterflies so far. It's from 2004 so yeah it's old but gold~ the leads were a IRL couple during this time which makes the chemistry even stronger! Lots of sexual tension, passionate kisses and even a bed scene! But its kinda dark as it deals with rape, mental illness...neverthless so far this drama has my favorite couple ever~
If you want something lighter, try Coffee Prince , this couple has also lots of sexual tension and great kisses!! Gave me lots of butterflies~
Something About 1 Percent is pure fluff, also passionate kisses. Very cute drama if you can stand ML's who are a bit controlling/ possessive. Its a remake of the drama 1% of Anything from 2003, I haven't watched it but my guts tells me its not as great as the newer version... one of the reasons being that back then all k-dramas was without passionate / realistic kisses