I went to Japan for about a month as someone with tattoos. I didn't have many issues out and about but I was told in the gym and I could not have them showing.

I just wore sleeves over them and although less comfortable than my normal gym attire it was fine.

I was denied access to an Onsen because I honestly forgot about the tattoo thing for a while but was able to find one that was tattoo friendly. They were not mean or anything they just informed me it was policy. Completely understandable given the history.

My tattoos are very noticeable though. Like you would never miss large forearm tattoos, so it's probably hard for them to overlook for them and let it slide even for a foreigner