The short answer
FlightVerified does not treat Japan as a destination with one blanket onward-ticket rule for every nationality and airline. Departure evidence can still be relevant, especially when a traveler must show that a short stay is temporary and that they have a practical means to leave.
What the official material actually says
The Immigration Services Agency lists a return air ticket as an example of material that can show a Temporary Visitor has the means or funds to depart Japan in certain status-related procedures. It also lists transport evidence when a person must demonstrate arrangements to leave.
What you should check before departure
- Whether your passport needs a visa for the intended short stay.
- The period of stay you are seeking or permitted.
- Your airline's document-check requirements before boarding.
- Whether any return or onward itinerary remains valid at check-in and arrival.
- Whether the next destination is one you can lawfully enter.
When an onward reservation is useful
Use one only when your actual travel context makes departure evidence relevant. A generic claim that "Japan always requires an onward ticket" is not a sufficient reason to buy anything.
Check Japan route