I agree with Lee - it looks authentic and you need specialist advice via his link.
From the pictures only - the hilt ornaments, tsuba and ray skin look to be of good quality and also the signature looks authentic. The second character is Hiro which is a common part of many Japanese names. I can't read the top one. Signatures can be faked of course, but overall the impression is of a real Japanese sword. Just my opinion though - and please feed back to us what the experts say.
The blade looks as though it can be recovered but needs a professional Japanese sword polisher - which is very expensive and charged by the inch so be grateful it's a short sword!
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