To change the title screen and in-game language of Hi-Fi RUSH to your preferred language, adjust the language settings in Steam.
How to Change the Language
Open your Steam Library and locate Hi-Fi RUSH.
Right-click on the game title and select [Properties...].
In the left menu, click [Language].
Choose your preferred language from the drop-down menu.
Restart Steam or relaunch the game for the new language to apply.