Quote from frustratedguy109

I'm not really sure if this fits the criteria, but in Glass Mask someone the main character hates falls in love with her.

In Special A, the main character falls in love with her rival... But I'm not sure if that's what you're looking for, since the love is mutual, and it's only a friendly rivalry.

The main character eventually falls in love with her antagonist, who later tries to maim/kill her later on in Hot blooded Woman.

I think Legend of Nereid meets your criteria.

In Threads of Time, the main character is a Korean who falls in love with a Mongolian princess when the Mongols invade Korea.

The main character in Tokyo Crazy Paradise is the child of a pair of police parents, who falls in love with a yakuza boss. Not sure if it's what you want, because they're usually on the same side...

Glass Mask is one of the most wonderful manga I have ever read! Unfortunately, I think it is dicontinued

I also want to add:
Tattoo of Angel - Chiho Saito
Magic Knight - Clamp (there's a twist in it 😀 )

Help! I'm looking for... manga with dangerous guys [url]http://www.mangaupdates.com/showtopic.php?tid=39874&page=1#post594033[/url]

Vampire Game. It's not a shounen ai at all as the database says.

What I like in Trivial Pursuit style. Pick your category:[img]http://i379.photobucket.com/albums/oo233/Reid4891/Manga/trivia-1.jpg[/img]

Hmm..there is the 2nd or 3rd arc in Chameleon Jail that has something like that ...I would love to say Majin Tantei Nougami Neuro but

Neuro appears just fascinated with Aya Asia not in love though the possibility is maybe probable if the mangaka suddenly decides it 😉 since ! reportedly, Neuro topped the good characters poll and Aya the villain's poll once.

[img]http://i221.photobucket.com/albums/dd199/vivharv/Gokusen-1.jpg[/img]

Quote from qiqi92sg

I believe Shugo Chara is going in that diretion.

yes!!! hopefully.
I <3 Amuto

i think Rough by Adachi mitsuru is a great example.
Its really funny and most of the time unexpected. And i loved the ending!!
Well there r no good/bad sides, nor supernatural powers. but its still a great romance to read ^^

"Cinderella's glass shoe was the perfect size.
So why did it slip as she ran?
It must have been to attract the attention of Prince Charming.
I dont see any other explanation" from Nana

I'm pretty sure Harukanaru Toki No Naka de is in that direction.

[img]http://i56.tinypic.com/acfmfo.png[/img]

Kilico is great.

[img]http://www.ponpokopon.net/Katsu1.jpg[/img]

I think Basara is good if you like adventure/action shoujo. She falls in love with the direct enemy and doesn't even find out until waayyy later.

♪MONSTARR~ will eat all your cookies and steal your bishies~♪ Φ_Φ

At the start the main female character doesn't know they are enemies as such but it does fit your criteria as it goes along and they don't like each other much at the start anyways and that is:
Royal Seventeen - I loved it

Quote from ranmaru

Kilico is great.

hated the ending