I'm from New Zealand and I am planning a trip to Japan next year. The flights I'm looking at have short layovers in Australia where I don't plan on leaving the airport so I don't think I need a visa for that, but will I need one for Japan?
As a New Zealand citizen you won’t need a visa for Australia as you don’t plan to leave the airport and will only be there for a few hours. If you do choose to take a longer layover (8+ hours) or leave the airport you can get a SCV visa on arrival by filling out a landing card.
You don’t need a visa for Japan either as you are going for 90 days or less, but you will need an onwards/return flight as detailed in Timatic, the database used by airport staff:
The following are exempt from holding a visa: Nationals of New Zealand for a maximum stay of 90 days.
Important: Visitors not holding return/onward tickets could be refused entry.
NZ citizen here.
You don't need a visa for Australia as you're in transit, and even to visit don't require one.
As a tourist in Japan, you need a flight/boat trip/etc out of the country, but otherwise can have up to 90 days.
Source: Have visited, transited and lived in Aus, and visited Japan four times, on a NZ passport.