The steps to add a Japanese input method depend on the operating system you are using. Below I will introduce ways to add Japanese input methods on Windows 10, macOS, as well as Android and iOS devices.
Open the Settings app.
Click on "Time and Language".
Select the Language tab.
Click on the "Add Language" button.
Enter "Japanese" in the search box, then select "Japanese" from the results and click "Next".
Select additional language features (e.g., speech recognition, handwriting, etc.) as needed, and then tap "Install".
Once the installation is complete, you can switch to the Japanese input method via the language icon on the taskbar.
Open System Preferences.
Click on "Keyboard".
Select the Input Sources tab.
Click on the "+" sign in the bottom left corner to add a new input source.
Select "Japan" in the list, and then you can choose an input method such as "Hiragana" or "Romaji Input".
Click "Add".
Switch to the Japanese input method via the input source icon on the menu bar.
Open the Settings app.
Scroll to "System" and click to enter, then select "Language & Input Methods".
Tap on "Virtual Keyboard" and then select "Manage Keyboard" or directly select "Keyboard" (this may vary depending on your device).
Tap on "Add Keyboard" and find and select "Japanese" from the list (may be required**).
Once added, you can switch input methods via the notification bar or by pressing and holding the spacebar.
Open the Settings app.
Scroll and tap "General".
Select "Keyboard" and then tap "Keyboard".
Click on "Add New Keyboard....”。
Scroll through the list of keyboards to find "Japanese", and then you can choose between "Kana" or "Romaji" type.
Once selected, when the keyboard is activated, you can switch to the Japanese input method via the globe icon key.
The above are the basic steps to add a Japanese input method in different devices and operating systems. If you encounter any problems during the installation process, it is recommended to refer to your operating system's help documentation or support resources.