I really want to read something that has a girl as the main - maybe, a detective or something~

Things like Detective Conan and Kamikaze Kaitou Jeanne are interesting~
So is there anything else like those? 😀

Kamen Tantei - not being scanlated, but all four volumes are out in English.
Zodiac P.I.
Crossbone Tanteidan - though there's no romance.
A Perfect Day for Love Letters - I haven't read any of this, but it looks interesting.
Ai no Joou - Read this recently, and it was pretty good. Kinda a pity it was only one volume.
Chicago - A really good one, I thought.
Tantei Revolution - Haven't read it, but it appears to be what you're looking for.
Kindaichi Case Files - Highly, highly, highly recommended.

Most of them seem really interesting! 8D
Especially the last one, so I'll most likely be reading that soon. Along with Zodiac P.I. which seems pretty cute. xD;

supergirl
Dazzle-very good, the main heroine is highly intelligent and works on mysterys in a very detective like way.

they are a little more serious, but kinda along the lines of what you wan't. hope they help a little.

edit: forgot to add Sweet Blood!- it is also kinda along the lines of what you described.

Definitely Spiral. The best detective manga ever, and even if the protagonist is a male there is a girl near him all the time. It starts slow but it became great very fast. Trust me, you can't miss it if you're a mistery lover.

Second choice is obvoiusly Spiral Alive (and could be something else? Of course no 😀 ). It's its prequel but you should read Spiral before otherwise you spoil most of the story.

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

The Case Files of Karasuma Kyoko <-- really interesting, but has no comedy/romance.
Ao no Fuuin <-- the girl struggles to discover the secrets of her past.
And i definitely second Spiral

Current avatar features Badou from Dogs.

If that is what you are looking for then I would recommend IO

It doesn't have as much comedy as some, but the story is incredible. If you like the ocean or if you have scuba dived then it is also a good choice. I particularly enjoyed it because I go scuba diving every time I get the chance, so I can relate with a lot of the stuff in the story.

Bloodhound
DN Angel
Underground Kids
Ghost Hunt

How about Deka Wanko?

Sounds like it's exactly what you want. Unfortunately it's just in raws at the moment, but hopefully some group will pick it up soon.

Forget Me Not

Faeries' Landing
Gekka no Kimi
Suzumiya Haruhi no Yuutsu

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Ah, I didn't think there'd be this many~
Spiral really caught my eye.
So, for sure, I'll be reading that with a few others<3

Thanks everyone. (: