Assuming you take a 777
Two choices to go from NRT-GUM
CO7 (737-800) departing at 1715 arrives 2150
CO964 (767-400) departing at 2040 arrives 0115
assuming you go on the 777 which arrives at
1545 on CO7 from IAH
1505 on CO9 from EWR
You will end up on a 737-800 if you do not want to wait at Narita for 5 hours.
Omedetto Gozaimasu
Kampai,
Klaxon