I booked a "Japan Free Return" flight departing Melbourne May 7 2016, however the online system caused me to book the return flight in the next month, I believe this was a trick.
The online system deliberately presented June 2016 dates for the return flight knowing that it would lead to mistakes so they could avoid providing the free return flight when people like me wanted to change it.
Also the online system does not show flight details on the payment page, obviously to hide any mistakes, so they can charge for changes or avoid having to provide a free return flight.
Furthermore I also included a "Plus Bundle" so I could change the flight, however this is useless because Jetstar says all the free return flights are gone, however that is ridiculous because I am holding one! I just want to change it, as in "Free change"! That's why I paid for the "Plus Bundle"!
Please be warned and be careful.