Set up a Japanese input source on Mac
If you set up the Hiragana, Katakana, or Romaji input mode, you can type in Japanese.
On your Mac, choose Apple menu > System Settings, then click Keyboard in the sidebar. (You may need to scroll down.)
Go to Text Input on the right, then click Edit.
Click the Add button , select Japanese (scroll down in the sidebar on the left or use the search field), then select any of the following on the right:
Japanese - Kana
Japanese - Romaji
Tip: The Romaji typing method is useful when you’re not using a Japanese keyboard; text you type is automatically converted to hiragana.
After you add a Japanese input source, you can change settings, for example, to select input modes or show predictive text completion candidates.