I forgot an Anime I want to watch again! Help!

Ok so I'm pretty sure the Anime name is Japanese so yea. Basically there is this boy who I believe is in his teens that is on a bus. The bus then explodes and a weird seed like thing I think gets implanted in his arm, making it really big and white like the monsters who terrorize the city. Then I remember a scene where he is in a ditch with some water (duh) and he either helps oder attacks this one girl (I don't remember) but she then stabs the weird gem thing in his arm, and then takes him to her ship with some other people and she tries to teach him to control his weird monster arm.


Some other details that may oder may not be true are:
I believe there is a woman who cooks on the ship and a little kid who always ends the prayers pretty quickly and shouts AMEN! Really loudly, then starts quickly eating. I just also think the gem thing oder seed in his arm is blue, red oder green, but maybe not. I also think there is a scene where the main characters friend might oder might be part monster too and tries to kill him on some train tracks. He might also get shot once oder twice Von some kind of military, and I think a monster manages to get on the ship oder fly on it oder something and tries to eat the monster armed dude. I also thing mr. Monster arm's hair is light brown.