2 hr connection at Narita
 

Our international AA flight arrives 4:40pm at NRT and we'd like to take the 6:30pm JAL flight to Osaka ITM. Is this cutting it too close? Unfortunately this is a last minute decision so Osaka would be on a separate ticket.

I think AA and JAL have codeshare agreement so if you missed the Osaka flight because of delays from AA then you will be taken care of - next available flight, hotel and meals if necessary. Just make sure you issue your ticket from the same source and have both the AA and JAL flights on the ticket.

I transit Narita all of the time, on my way to Bangkok. You should be fine with 2 hours transit time.

You will make the connection unless your AA flight is more than an hour late. However, if the flight to Osaka is on a separate ticket, JL would have no responsibility to honor the NRT-ITM flight that you missed.

The 6.30 flight to Osaka is the last flight of the day from NRT. So, even if you were put on the next flight, that flight is not until the following day, from a different airport. JAL has only 2 flights/day from Narita to Osaka, both in late afternoon.

Unlike connecting to a Bangkok flight, the OP must go through immigration in Narita. The Japanese are generally efficient, but late afternoon is peak time at NRT for international arrivals, and I've waited as much as 40 minutes to get through the line. But, as long as the incoming flight is reasonably on-time, you have no worries.

The last train that you could take from Narita and still get to Osaka (or Kyoto) is the 7:46pm Narita Express, connecting in Tokyo to the shinkansen train to Osaka and Kyoto (arriving around 11.30pm).

If the OP did not have to pass thru immigration then 2 hours might be ok. However I would want at least 3 hours knowing 1) the first flight could be delayed, 2) immigration lines could be long, 3) JAL and AA may be in different terminals.

Thanks all...will need to think about how to do this. First step is to call AA to see if they would change our award tickets to include Osaka. Or spend a day or two in Tokyo then take the train to Osaka. We have only 6 full days available which also includes the day we need to get back to NRT...so 5 maybe 5 1/2 days of touring.