Teizokurei Daydream aka Vulgar Ghost Daydream
If you would ignore some tits and S&M actions, this is one heck of a horror manga (consider those as a fanservice). The person scanlating it said that he's working on the final book and expected to release it at the end of 2010.

Mail
About a spiritual detective who exorcise ghost using guns.

Kurosagi Shitai Takuhaibin
Made by the same guy who wrote Mail, this one is packed with laughter and horror. About a group of people who communicates with the deceased and tries to grant what the spirit wished them to do.

I know that all those above aren't exactly supernaturals vs helpless mortals like the op requested, but maybe you would like to have a shot on those titles above.

One Missed Call
Friends said that the flick is more scary than this, but I find the manga is scary enough that I didn't dare to watch the flick.

Dark Water

I don't know if the titles I give will suit your taste. Just check it out
Book Club
Gaki Jigoku
Manhole - this is a pretty interesting manga although it's labeled as mature because of some naked scenes. No sex or any kind in the manga though.

I second ihateregistering234's recommendation of the manga One Missed Call. It sure is creepy.

Thank you guys- I'll be sure to try them out! 🙂

This may or may not fit: Hyakka Teien no Higeki It's more slightly psychological + surreal than horror, really. 😛 But it most likely won't fit?

Quote from satoshiyasuaki

I don't know if the titles I give will suit your taste. Just check it out
Book Club

Book Club is the first manga that made me cover my eyes while flipping the pages. You should definitely check it out.

[color=black]Does not compute.[/color]

the only one i can think of is highschool of the dead it has romance and harem ino it but from what i've read there have been maybe 3 or 4 moments the most

@VampireBanana -
Wow- that manga looks nice! I love surreal psychological thrillers!

@purplegeass -
Thank you, but I already tried Highschool of the Dead (and didn't like it at all). Thanks for replying though.

Ghost Hunt 😲

Btw, I'm not sure if you read online comics but you can also try this: What birds know where romance is kinda secondary, don't worry. And the horror comes first.

http://fribergthorelli.com/wbk/index.php/comic-archive/

Hope you liked Hyakka then. 🙂

Also, if you don't mind psychology that serves more like horror(if scary little girls can horrify...lol), also try this movie: Bad Seed(1956 version) A shame the ending was ruined by American censorship laws.

http://www.imdb.com/title/tt0048977/

Also, maybe Kare no Satsujin Keikaku
reset perhaps.
Hanshin More like psychology that serves as very very light horror.

And errr... I know this is kinda off-topic but if you like something that's interesting, try this Violence Becomes Tranquility

@sirabc -
Thank you, I already read Ghost Hunt. And yeah, I love it!

@VampireBanana -
You keep recommending me such cool stuff! Thank you so much! I'll be sure to try them all out.
Well, except for the movie, that is. I don't live in a Western country, and stuff like horror movies are not really available where I live.
And- yep, I thought Violence Becomes Tranquility was pretty good- kind of unexpected considering the description.

Thanks again!

sankarea - im sorry and i know that you asked not to suggest manga with romance as most of the plot but for this manga most of the plot is kinda horror based and this is one of my favorite manga ATM

@Calstine: Well, it's good if you enjoy them and it's okay if you don't. 🙂

Anyways, hope to see you around sometime... poofs off