Please refer to the following:

1. Click the "Settings" icon on the initial page, as shown in the following figure.

2. Click to enter the setting interface, and then click "System", as shown below.

3. Click "Language and Input Method", as shown in the figure below.

4. Enter the language and input method interface and click "Language", as shown in the figure below.

5. Enter the language preference page and click "Add Language", as shown in the figure below.

6. Find "Japanese" and click to add it to the language selection, as shown in the figure below.

7. After clicking, it will automatically jump back to the language setting page, and click Add Japanese.

8. Successfully set the language to Japanese, and goole play moved to the Japanese area accordingly, as shown in the figure below.