Maybe people already used these names, i dont have problems with latin names.
Also there is no need to change you system to japanese to create your account, but you need to change it to be able to play the game anyway. Not only the non-unicode language but also date and time formats or else it wont load most of the graphics except the UI.
I use this to type japanese captchas:
http://www.hp-gramatke.de/nihongo/german/tab0005.htm for Hiragana (Arcadia account creation uses Hiragana)
http://www.hp-gramatke.de/nihongo/german/tab0006.htm for Katakana
ps: Something totally different, i was looking for the hanbiton mythos website and found a german site named hanbit.de. Its completely in korean and about a korean church community in cologne, germany. LOL