Ok, scratch that. The reason I was never able to join her is because she was spending most of the time in Ranked mode. Today I texted her and asked her to just play a normal Turf War so I can test and get a definitive answer if I'm able to join or not. I was able to join. We played a couple of hours of Turf War and Salmon Run with no issues except a little bit of noticeable lag now and then, but it wasn't constant so it didn't make it unplayable or anything. I don't see why Nintendo region locked it to begin with, they could've at least gave an option of Worldwide or Regional like in Mario Kart.
TL;DR = Yes, as long as you are friends with a Japanese player you will be able to join them and play with other Japanese.
TL;DR = Yes, as long as you are friends with a Japanese player you will be able to join them and play with other Japanese.
Last edited by Antisocial,