Like Chinese people, Japanese names are also divided into two parts: surname and given name. For example, Nakajima Mika, Nakajima is the surname and Mika is the first name.
However, when the Japanese government registers names, generally speaking, the surname must be registered in Chinese characters, but there are no special regulations for names. Kanji, hiragana, and katakana are all acceptable. As long as it is not particularly exaggerated (for example: Nakajima Devil × )
Artists are highly free in their stage names, and they can come in any form, so they should be listed as exceptions.