NO ECCHI!
NO YAOI!
NO MANHWA!

You know how most of the times mangas don't give you a reason for why the protagonist is so amazing, great, genius, etc? Why did he win or loose, no one knows. Nor does anyone know why he is labeled one in 10 years.

I want it explained. Like, for sword skills, I don't want them just waving their swords around according to special effects. I don't want to see them swing and suddenly earth splits apart. I mean, he's cutting air, it's not physically possible that the earth splits if you don't somehow summon an earthquake, right? So for sword skills, I want to see them winning by skillfully using the laws of physics. I want to see them DODGE! That's the very basic damn it! Parry the enemy attacks, footwork, turn enemy strength into his own, etc! That make sense? I mean, martial arts does exist in real life, so if he's not a mage, don't make him look like one.

Or, for things like sports. You often see them yelling out a name "blah blah blah!!!" and suddenly the opponent is defeated. Makes you think there is no skill involved.

It doesn't have to be martial arts or sports, just giving examples. Those two are especially bad in this area with the overuse of special effects.

In short, I don't want the plot ruling over the skills. I don't want the chars to win or loose only because that's part of the story. I don't want to see them defeating the demon king n times stronger only because of the plot. I suppose this might be better defined in animes? Considering there's animation rather than snapshots like manga panels. But either is fine.

Some examples, though to be honest, I don't remember myself how much they fit.
Liar Game (drama)
YuGiOh (anime)

Bad examples:
Phi Brain
many, many martial arts and sports manga

Prince of Tennis, the original anime series is one of the better sports, but went completely downhill for all of the sequels.

[img]http://www.nodiatis.com/pub/19.jpg[/img]

i know your pain bro. But mental aspect is a key in sports, but there are a lot that does it really well, shounen magazin is amazing for that.
Reccomendations:
Tour(short but the one of the best, and there are no suddenly power up, got me tottaly addicted to cycling)
One outs, same author of liar game.
Last inning, the best baseball manga in that aspect
Gigant killing, there a lot into mental aspect of the game, but it's not i win my friendship power nor tsubasa like super skills.
Daiya no A, really well done baseball manga, and get better as it goes, a lot better.
Baby Steps, the protagonist uses his tactics to compensate for lack of experience.

The world god only knows protagonist uses dating sims experience to get the girls
slam dunk uses basics to beat experienced players

I like turtles

I've already read One Outs and Last Inning. Loved One Outs, one of the best sports mangas. Didn't realize it was the same author as Liar Game though, since the art was a lot better. I only watched the drama of Liar Game since the art was unbearable...

I got recommended Baby Steps quite a few times already, just never seem to get very far in it. As for The World God Only Knows, always thought it was ecchi, but guess I was wrong.

Will check the others out!
Isn't there any non-sports mangas though?

[img]http://www.nodiatis.com/pub/19.jpg[/img]

Watch Sword Art Online, the Anime, and if you don`t mind Novels you can also read it^^, and in holyland they explain the moves the MC makes

I know exactly the right manga for you. Holyland the art is not that great (it's good to me at least but I guess if liar game was unbearable for you, you'll find this one challenging) and the manga is wordy but it has every thing else you want.

All-rounder Meguru is very realistic in that regard.

Baby Steps is exactly what your looking for, mc uses his brain + practice to win, and he doesn't always win, it is the most realistic tenis manga i've ever seen
edit: forgot to say Over Drive another good 1 following what you want

stupid photobucket, wanting $400/yr just to display your images

Ookiku Furikabutte I'm pretty sure this fits, but I haven't read it in a while.

Teppuu

Quote from mybackhurtz

Teppuu

Seconded. Highly realistic martial arts.

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Kurogane (IKEZAWA Haruto) is a sports manga (kendo). Protag has a ghost as a master but that's all the supernatural it has.

Is this me in a nutshell?
Pretty much.
[img]http://www.dragonflycave.com/wpay/ninetales.gif[/img]

blood and steel city of darkness a lot of chinese manga do what you are looking for

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Red Eyes
Gunka no Baltzar
Jiraishin

Moonlight sculptor(Novel). This novel really explains as to how the main character wins his enemy to the finest detail. Of course if you do nto want novel... Then:
Historie
BabySteps
Kaiji

Are a few mangas that you may like.

"you must prove more patient than a caterpillar, more willing to survive than a cockroach, and more stubborn than a leech - or you will definitely fail" - Counselor Rodriguez, the Star of Wisdom