Oh for fuck sake. Why in the hell did you need to give him a bloody katana. Its stupid, Its pointless, Its cliche, Its out of place, and most of all, Its simply a sign of a groupy giving into Japanamania.
The fi was ok apart from that. Unfortunately that katana spoilt the whole thing. Really, why, why, would a wizard, you know, someone that can use magic, need a sword? Magic works...well...magic. It can do anything. Why in the name of whatever deity you believe in would he need a SWORD?
And if, for some strange reason, he does need a sword. Why would it be a katana? He is the head of 3 ancient British wizarding pureblooded families. If he was going to get a sword out a family vault, it would be a broad sword of some description, a sword of fine BRITISH history, not JAPANESE. To have a JAPANESE sword in side a vault belonging to a proud pureblooded BRITISH family, is stupid, and shows simply that you are willing to do anything you possibly can to have Harry turn into something one would expect to see in some sort of bloody Japanese anime or manga.
Its a pity, the story had promise, but you HAD to wreck it.