I've read about everyone buying their Sony noise cancelling headphones in the NRT duty free stores. Never having been to NRT, I was wondering if it is possible to get to one of these stores during a UA connection on my run to SIN? Or do you have to clear customs or is it otherwise inaccessible in the few hours I'll have?

Thanks!

If the headphones are in the duty free shops, they are located airside. Therefore, no need to clear customs and immigration to access these stores.