Upvote:5
I will be getting a tourist visa on Aβs passport for my vacation,
That's not necessary. You can leave country A on passport A and enter Japan on passport B and then keep using passport B for the rest of your trip, until you make it finally back to A.
At the airport in A you present passport B to the airline for check in but you present passport A when you go through exit immigration.
Example: I have US and German passport. When I fly from Germany to the US, I use my US passport to check in for the flight, use my German passport at exit immigration, and then use my US passport again for final security checks at the gate.
That's all perfectly normal and accepted unless one of your countries has issues with dual citizenship.