Hi Ari94,
I am Dave, I will help you with this.
If your Windows 10 is set to use Japanese as the language, you cannot change the 3D Builder app to use English, it will automatically use the Windows UI language.
It is possible to do that with the Microsoft Office apps, because they have separate language packs that can be downloaded and installed, but the Widows UWP apps do not have separate language packs