1. Right click on the game executable.
2. In the context menu that pops up should be an entry that says "Locale Emulator".
3. Go to that context menu to expand it.
4. Select "Run in Japanese".
View attachment 3522570
The UI is not translated. It will still be in Japanese but once the game starts, the dialogue itself will be translated. The UI not being translated is mentioned in the OP.
As noted on the
You must be registered to see the links
page, this game supports a namable protagonist. You can enter the family and given name of the protagonist on that screen. Select the entry on the left to leave it as the default. Select the entry on the right to reset whatever you typed to the default value.