I will be going on a company trip to Singapore this year with departure from SFO. I see that ANA has flights with layovers in NRT and was wondering how I can request for a stopover there (would like to spend 2-3 days there if possible).

Since it will be through my company, I will be booking flights through my company's travel agent, and this is not going to be an award flight.

Would anyone be able to provide some guidance? I tried searching extensively on this but details seems to be rather murky and remains unclear to me...thanks