My mother frequently picks up children's books (traditional books, Western comics, and manga) for my little brother at the local library. Whenever these books happen to be manga, I skim over them because 1) supposed "kids' manga" is often more violent than one might think, and 2) sometimes, "kids' manga" is really great.
This is a little bit of both of those things.
Bakegyamon (Backwards Game) is a manga whose history I know little about. All I know is that I've read most of the 52 chapters. It's a complete little weekly manga. It's mostly pretty silly, especially towards the beginning, but it really picks up in the last two volumes. (I read it in a five volume format; apparently the local library missed volume 3, but I don't care.)
NOTE: Spoilers abound, although I don't think I'll spoil anything I can avoid.
Like many modern "kiddie" anime/manga, Bakegyamon heavily features monsters in the story. Predictably, its protagonist is a kid wearing a black shirt, jeans, an open vest, and a backwards cap, i.e. just like the Pokèmon kid. Whereas Ash Ketchum is an obnoxious little guy who endorses a fancier version of cockfighting, though, this kid, Sanshiro Tamon, didn't accept the status quo: When he learned that the monsters were people too, and had been enslaved for the purposes of this game, he decided that he would use the game's tournament prize, one unrestricted wish, to free them.
However, a previous winner of the game, whose wish was that the game would go on forever (sort of), learning of his plans, decided to eliminate him from the competition by sealing him into one of the cards that the monsters are (predictably) bound up in. There's a game rule that only monsters can be summoned from the cards, so he's trapped forever.
Unless the being who holds the tournament and grants the wishes, and who has despairingly watched it spiral out of control, turns him into a monster.
The problem is that being turned into a monster will probably kill him.
But, even presented with the opportunity to live in a dream world where it will be basically lucid dreaming forever instead, he'd rather risk his life than sit by.
And so, he gets accidentally summoned by one of his friends who's trying to defend herself from the villain.
Some manga artists can and will draw the heck out of anything. This guy is clearly one of them.
Anyway, since he's now a big... thing, the mere fact of his being summoned blocked the villain's last attack.
The villain, annoyed, states that even though he must now be a monster, there's no way a runty monster like himself will stand a chance against his enhanced high-class monsters.
I've read that this will be made into an anime. If this doesn't get a "FALCON PUNCH" meme video, there is no justice.
Predictably, Sanshiro's gigantic fist sends off the villain's monster on the Team Rocket express.
Then Sanshiro's arm falls off.
Yes, his arm falls off. The stress of using his monster powers so soon after being transformed is making his body fall apart, and his arm just snaps right off. (It's depicted like shattering clay, so it's not gory, but it is hardcore.)
What does Sanshiro do next? Keep in mind, this kid is eleven, and his arm just fell off. Most people, much less most kids, would be screaming or passing out at this point.
Well... (Note that it reads right to left, if you're not a regular manga reader.)
Then the villain sends in another monster to attack again. What's Sanshiro's response? (Once again, right to left.)
He does it again.
When the villain sends in a third monster, his response is to grow a new arm and do it again.
He's basically the best kid character since Daiya from Gaiking. (Actually, this manga originally ran just a couple of years after that Gaiking series aired. Hm.)
And I'm not sure that was actually the most batman thing that Sanshiro did. (If you want to know what else he did, go ahead and read it yourself. Going through the somewhat less interesting earlier chapters to get to this one is worth it.
And if you don't know why I use the word batman like that, there's an explanation here. The actual why is because I don't swear except by accident.)