Next month I'll be traveling to Japan with my wife and two children. Our youngest (1yo) is still in diapers. I read a few guides about traveling in Japan, and saw mention that change tables are sometimes placed only inside female restrooms.
This is true for other parts of the world as well, including where I live (Netherlands). Even our local McDonalds has a changing table in the female restroom. I tend to ignore the gender sign and just walk in there if I need to change my kid's diapers. Most women seem to understand that it's not my fault that the table is in 'their' restroom. This remains true even if my wife is also present at the restaurant.
Now, the question: how can I best approach a similar situation in Japan? Should I ask my wife to do it if she's there? And what if she's not there? Should I ask the staff what to do? I mean, that can be problematic since my Japanese is very limited.