Recently I just watched G Gundam and I liked how much Domon was dependent on his attachment to Rain. Like he would go completely mad if she wasn't there with him.

Are there mangas, where the guy is just dependent on the girl being with him?

The romance should be pretty evident. (Kind of like 100% Perfect Girl)

Thank you in advance!

Kanata Kara - Fits very well.

but shes also very dependent on him i dont think it really fits
please save my earth-i think the guy would have gone insane if it werent for the girl
maybe Hakuji
kare kano though the story starts to focus on his past towards the end(last 5 volumes)
Watashitachi no Shiawase na Jikan...maybe

Try Metronome (LEE Won-Jin), It's a webcomic. The guy lost the vast majority his memory, but that's okay since the only memories he has are of her and that's all he needs.

Whoa!! needed to fix that quick. Without the author in there it leads you to a hentai.

The Breaker Don't know if that's what you mean but:

But you can't really tell until it reaches that point (that he would go insane without her I mean).

Also I second Kare Kano.

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Third on Kare kano

Alive - but not the protagonist, the bad guy is the one with an unhealthy attachment with the girl

Metronome (LEE Won-Jin) - Seconded! I just read it, and that girl is his life. He would kill for her.

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The OP didn't say anything about not wanting the girl dependent on the guy. And though she's dependent on him in general, she doesn't go mad like he does when they're separated.

All in all, I'd leave it up to the OP to decide whether it fits what s/he want.

Issho ni Neyou yo The guy is very attached to the girl. He's not really mentally stable but he really needs her. Its very cute but dark at times. Its a good read and is still ongoing.

Pumpkin Scissors perfectly fits..

Goong seems to fit (both the bad an the good guy are like that)
Love Celeb may be ... (just a little warning, if i remember well a lot of the story contains smut)

All of these sound great!!

@Blique= as long as the guy goes ballistic, i'm completely fine with it. even though the girl does love him equally, i just wanna see him lose it. so yeah, it does fit =) thanks!

@sarah-eats-cupcakes = please save my earth sounds interesting, so I will be checking that out too!

gahh, i'm excited! keep 'em coming you guys ( if there are more )

thank you again to all of you!

well, it's a visual novel, but since i just finished it, plus it meets your description...
here goes: Saya no Uta


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its cold down here fam ~

oh okay then
sorry @blique !