You are so frustrating .... Read me post clearly.... Work USA SEL, then LAYOVER! Next day, SEL NRT turn around, then LAYOVER! Then work SEL back to US last day. There is no multiple leg segments. A 4 day trip is made of it. Same could be done with KIX or NGO.
I am questing our crews safety laying over in NRT/HND. European airlines have modified their OPS.
I may be frustrating, but it's increasingly obvious you don't know much about airlines outside of nonrevving, EPT's and delivering a meal service, much less all the stuff that goes into getting an airport operation up and running for an airline. Opening airports for AA was one of the better jobs I had. Scheduling & planning cabin service for international airports was one of the worst.
Crew safety is definitely a first priority, but there's a lot more to be considered that you seem to be totally ignorant of. Like the entire ground operation.
European airlines have a much easier option with SEL being along the way. That greatly reduces the impact of flying the tag somewhat, and those airlines also probably have personnel & ground handling already set up.
The options along the way between the US and NRT are much more limited, and will require setting up ground handling. Not a big deal, but still takes time to arrange.
Then there's customers. Remember them?
Flying time to/from the US to any of the points except CTS will be a wash but then you have to factor in the time for backtracking/sidetracking over to NRT.
At some point you still have to clean, cater and security check the airplane.
With the added flying time of a tag, plus time for two crew changes, and you've now added anywhere from an optimistic three but probably closer to six hours to the arrival time back in the US. That is probably not a big deal for the non-connecting customers, but it could screw up a lot of connections.
All in all, lots of considerations at play. It's not just as simple as deciding that you're going to start flying a new routing tomorrow and hope it will all work out.