I found a flight that has a connection in Japan that’s cheaper than a direct flight to Japan. Is it legal to take that cheaper flight and leave the airport at the layover location as our final destination? Will they prevent us from taking the return flight?
It’s not illegal to pay for a service you don’t use or only partly use, provided the service itself isn’t illegal. It’s not unethical either; you paid the full price requested by the airline.
The airline may cancel your return ticket and blacklist you, leaving you stranded. Definitely unethical, but since it’s legal corporations aren’t too worried about that part.