Originally Posted by
allset2travel
As said up-post. No, you can't transit NRT.
Looking at your ending itinerary, you can only have 1 stopover (either at SIN or at HKG, but no both). Note that you have 3 segments in Asia already.
Why only one stopover?
-LHR-xSIN-xHKG-NRT would be valid assuming no other stopovers in Asia at the beginning of the journey. (subject to maximum segment rules).