Ok, let's discuss about the secondary character names. These are their Japanese names:セト
"Seto" is probably correct, but セト can be "Set" too, but never "Seth" (セトゥ), because the kana is slightly different. If you look at the Field files in the translated version (most specifically SETO1), "Seto's Wall" was translated as "Cet Wall". However, I have two clues that led me to believe that "Seto" is intended: because of the name of that file, and because Nanaki is a Japanese-like name; so Seto's name should be too.
E RE NO A
This is Eleanor, Dyne's wife. Apparently, it looks correct, but her kana looks a little like Rinoa's (リノア).ミーナ
This is Barret's wife, Myrna. "Mina" seems too Japanese-like, but "Meena" is another possibility.エルミナ
E RU MI NA
This is Aerith's mother, Elmyra. "Elmina" kinda looks Japanese, maybe "Elmyna"...?ガスト
GA SU TO
This is Professor Gast. I guess this one was mistranslated. Judging by the spelling, it could be "Gust" or "Gusto"; but no way I'll change his name to "Gusto", that'll make me think he's Spanish (makes me remind the Me Gusta meme lol).シエラ
SHI E RA
This is Shera. Her kana implies that her name was supposed to be "Sierra", not "Shera" (シェラ). The difference between them is very small.グリン
GU RI N
This is Choco Bill, the owner of the Chocobo Farm. I guess the transliteration for this one is "Green".グリングリン
GU RI N GU RI N
This is Choco Billy. Naming him "Green Green" is just dumb.クリン
KU RI N
This is Chole, from the Chocobo Farm too. No idea of how it should be. "Kreen"...?エスト
E SU TO
This is Ester. Judging by the kana, her name is possibly "Esto". But I've never seen a girl with such a name.
We can still discuss about the enemy names too. It's not finished yet.