Originally Posted by Mttrnd

Check out this thread:

https://www.flyertalk.com/forum/japa...s-edition.html

No problem with transiting with separately ticketed flights on ANA - done this through HND and it was alarmingly straightforward. They issued both boarding passes, through-checked baggage, etc., without any hassle as if it was all on one itinerary. There are no transit requirements for Japan. They check Timatic for the requirements of your final destination only.

Transit on different airlines is allowed but I would plan for more explaining, resistance and general hassle. Even if you have done everything correctly, all it takes is one spooked check-in agent to put a brake on your travel plans. They don't want to get caught out flying you to a country to find out that your onward travel plans with a different airline are duff and you can't enter the country.