1) Why and what brings him to Mahoushima? The main setting of the game is Mahoushima, which is not a part of mainland Japan.
2) How is his crossbow a gun? Are you trying to make a hybrid weapon because if so, I'm going to say no. A crossbow is in the bow category.
3) I would say another weakness for him since his GS has been raising him is that he relies more on the wisdom of his GS than his own wisdom.