Hi! I'm back again. This time I'm looking for some manga/anime which deal with an organization that train a group of children to become cold blooded killer. I will take any genres, although I do prefer the main character to be in the group of children that are being trained.

Some examples are:
L-Elf from - Kakumeiki Valvrave
Gunslinger Girl
Rolo from - Code geass lelouch of the rebellion

6 no Trigger
Anonymous
Number
Young Gun Carnaval

There's an organization of assassins in Arachnid too, but I'm not sure if they take in children specifically, and the protagonist isn't a part of it.

Red Raven, Akuma no Riddle, Scuro, and Tista are also possible fits because there are assassins and organizations involved, but I'm not so sure about the "child soldiers" bit.

Husk of Eden also could work because it's all about child soldiers, but they aren't really being trained to become "cold-blooded killers." (More like cannon fodder, actually.)

On the anime-side, the Gundam series do this a lot. Actually, just pick any Sunrise mecha series and, chances are, there'll be child soldiers in there somewhere.

Gun x Clover - somewhat fits. They are fighting against a group that consists of children who have been brainwashed into becoming cold-blooded killers. The group (called 'Child Room' coincidentally) has JUST been introduced though and it seems to be a monthly release so you might wanna wait a little bit.

Try this
http://www.mangaupdates.com/showtopic.php?tid=17376

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Round 2

Rose Hip Rose -The girl was from the organization, but i think she ran away or something...

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One of the main characters in Jormungand is a child soldier that is recruited into a gang of mercenaries. It's awesome.

You probably know this but... ANSATSU KYOUSHITSU Not exactly cold blooded but it fits

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