Before the pandemic, I went to Japan for 3 weeks and my cellphone was absolutely a lifesaver.
I went to a lot of city where I would have been lost without Google Lens, Google Maps, HyperDia for trains, "Japan Official Travel App", etc.
But with it, I've traveled accross less touristic cities and I was feeling confortable visiting local places without ant knowledge of the Japanese language beside a few words.
I would never dare to do that without my phone.