If you are squished between two fat people, you used the wrong jet bridge or turned right when you should have turned left. Plus you probably missed your chance to board first, when Sky Priority was called. No worries, boarding with the masses didn't cause you to miss any free cocktails in the Economy Cabin pre-departure service; because that's not a thing. More Bombay Saphire for the folks surrounding your empty lie flat seat up front. BTW, the flying pilots will enjoy that as a break seat or dining spot. And since you were oblivious to your boarding card stating Business Class, you probably missed step one after passing through KCM: tasty appetizers and drinks in the Sky Club, because "you somebody" for that leg at least.

Or, you could do it right, and avoid said oversight. Arrive in Japan rested from pampering, and head to the Radission for continued time zone acclimation.

Much of that in jest, but seriously, overwater DH deviation is one of the bonuses built for enjoyment. Take advantage. Iron man same day deviation is not for the faint of heart. If your push returns to the gate, you're missing your NRT outbound. I'd say 3/4 of the time gate returns still operate, but many hours behind schedule - sometimes after a crew rest. I've done same day in a bind, but there's not much "sit back, relax and enjoy your flight." Save the bonus day off for the trip home if you're blessed with that too (XCM menu for that booking).