Personally, Ms. Rosa, I think "Tethys" *is* what the developers intended, because "Tethys" is a mythological name, of a Greek nymph or dryad or something, as I recall. The reason I believe this is because I've seen the EXACT same katakana name in other videogames...the protagonist of Bounty Sword has a nymph helper whose katakana name is EXACTLY the same--the Te thing, another Te thing, a mini version of that vowel thing, and "su." The fact that the same name shows up in multiple games (and given the fact that Bounty Sword's Tethys is a fairy, like the mythological one, sorta) indicates to me that "te-ti-su" is how the Japanese represent "Tethys." ^__^