Why do people have hiragana and katakana in their names?

Some writing methods correspond to multiple reading methods, and some reading methods correspond to multiple writing methods.

take for example

ゃかぉり, かぉる

かぉり :かぉり, Jia Zhi, Xun, Li Xiang,,

According to Japan's household registration law and related regulations, Roman characters cannot be used in household registration.

many-to-many ...

Just like hanyu pinyin.

However, some Japanese names have no Chinese characters.

When sinicizing, find a common name with the same pronunciation.