Upvote:4
Passenger is always in charge for a visa he uses to get aboard, as airlines are responsible, well, for flights, not for border controls. One need to check all the info in visa to plan a trip. Your friend should probably notify Japan' Consulate about plans to visit some other country during visiting the Osaka, so they'll provide non-single entry visa for him.
And airline had no chance to check your friend visa during boarding the plane to Indonesia - they may don't even know his plans, maybe he don't want to get back in Japan.
Also, many countries do fine the airlines who allowed to board a person without a valid visa. Such situation can happen, for example, in Europe, when person goes to USA without proper visa - you simply can't check-in to flight to USA in such case.
Moreover, your friend may got some troubles in case of landing in Japan without visa - like even bigger fee than tickets cost, or get into jail for some time, or adding to the Japan' visa blacklist.
Upvote:13
Your friend is responsible - he had a single entry visa, and tried to enter twice. It is entirely down to the traveller to ensure they get the correct visa.
I'm surprised the airline allowed him to board in Indonesia, but even so, they'd only have to take him back there, not back to his home country - and he'd have to pay for it.