So I'm tired of trying this weekend.
NATASHAOTOMOSKI --> SATOSHINAKAMOTO
is a permutation cipher. I've known this for a while. Here's the key:
e b c h m f o a d n g k j i l
Here's what I can't figure out. If the remainder of the phrase is also a permutation cipher, how do we extend this key? It does NOT work for the entire phrase.
If we can figure out the key for the WHOLE phrase, that'll give us the full translation for whatever the ?.txt file might be.
Someone skilled in decoding might have some ideas. Let's keep this going

edit:
E B C H M F O A D N G K J I L
5 2 3 8 13 6 15 1 4 14 7 11 10 9 12
S A T O S H I N A K A M O T O