Currently there are three CJK fonts available in StarLing: two fonts for Chinese (traditional Big5, simplified GB) and one for Japanese (SJIS). These fonts are summoned from the editor by pressing F2; to switch between them press function keys (F1, F2, F3). The characters can be chosen by their modern reading.
The Japanese katakana / hiragana letters can also be chosen from the menu, but there is a keyboard shortcut: if you press Ctrl either before pressing F2 or after it and type the syllabic value of the letter, the letter will be input directly into your text without any menu choice.