You shouldn’t need a VPN to access Smartnews. I can download it through my American App Store. Once you have the app installed, you’ll go into settings and change your region to Japan (it should be at the top). On ios you can also change the app’s specific language (interface) to Japanese in system settings, I’m not sure about Android though.
edit: just read what you said about the French app store. You’ll probably need to make an account in a different region and then download the app through that account. At least for Apple, you don’t need a VPN to create an account in a different region. It might be a good idea to make a Japanese account if you want to download other Japanese apps, otherwise, US will work for smartnews.