I'm trying to locate a manga about a this guy who is in high school and he is not really popular, to the point his whole class doesn't invite him to their Xmas party.
At the Xmas tree, in the town square, a monster destroys it. This girl with super-powers come and saves him. A day later, the monster comes back but it turns out the guy can control it and it gets stronger the angrier he gets, kind of like the Hulk, but this one acts like a dog and is separate from him. He works with the girl with powers so that they can stop his monster that she DOESN'T know that he is controlling
The reason they have powers is due to something called magic bullets or world bullets or something like that