looking for any romance manga/manwha with obsession..like the main characters are way into each other..

The only thing that comes to mind is The Flowers Of Evil.

Watashi no... Megane-kun is the first thing that pops to mind

sort ofs:
Desire Climax
Cinema Empire
Ren'ai Shijou Shugi-mostly other people obsessing over the main couple

Is shounen ai/yaoi ok?

Well, you say you're looking for any romance and didn't specify against anything, so here's what I have to suggest. All are yuri:

HEN - somewhat one-sided obsession
Honey Crush - completely one-sided obsession.
Iono-sama Fanatics - Most supporting characters obsess over lead, lead obsesses over certain supporting characters.
Tetragrammaton Labyrinth - haven't read much but one of the leads seems obsessed with the other.

________________
Tree + Taco = Tree taco.

Bitter Virgin

________________
What I like in Trivial Pursuit style. Pick your category:

School Days

lol

Only one of em is deeply into the other one...but still...

Nice.

haha..if you want something more obsessive watch the anime

________________
i was nervous at first it was big & long & went straight up i had to try it i eased onto it & liked it! i went up & down on it.... i love escalators now!


(great onizuka ftw)

Second [m]The Flower of Evil[/m]
Fetish Has a few obsessive romances in it.
Goth - not a romance really, onesided maybe.
Die

Pheromomania Syndrome
Lawl. Hillarious manga, and you can say that both main characters are way into each other...to the point of slaughter nosebleeds caused from perverted thoughts, relax, its just a gender-bender shoujo manga. XD

________________
"Beware How You Take Hope From Another Man."

hmm.. only one i think about is hen

that's pretty much beyond obsessive and into mental

Hana ni Nare!

Hakuji
System of Romance
DOLL: IC in a Doll
Crimson Cross

and I TOTALLY second Fetish.

________________

The Hidden Agenda=Gol.D.Ace

This Week's favourite:
DoLL (Okado Tatsuya)
Xp