This was a very good story and I enjoyed reading. It's well written and the imagery is great. However, just a few technical things:

"masterless samurai" is an oxymoron, as samurai basically means "one who serves". What you want is, "masterless warrior". a ronin is no longer a samurai.

I also want a VERY good reason why he killed his master. Back then, things like that were unthinkable, and this sounds too matter-of-fact about it. Also, a ronin would not be allowed near any villages or dojos etc, unless they were run by other ronin in seclusion, which this story doesn't imply.

"but the only sword we have is an old sakabatou- a reverse blade sword!" - would someone actually say that? It would be common knowledge what a sakabatou was, so it's very unrealistic and contrived that she went on to define the word.

Furthermore, the reverse blade is NOT a historical sword. It would have been extremely difficult - nigh impossible - to forge. the reverse blade sword is a modern novelty. But that's just if you want historical accuracy.