Originally Posted by Plusflyer

They indeed issue some kind of "transit authorization". It's a hexagonal stamp in the passport and it can take several minutes to get it. It's a separate queue from the regular immigration but it can take as long as the regular one.

I did a transit in PEK to NRT once and it's quite a lot of waiting and walking large distances. I don't remember exactly how much time it took me gate to gate but it was of the order of 45 minutes.