Are most flights from Australia to Japan staffed by hosts with good Japanese language skills?
I assume that Australian based airlines would, but I'm not sure about airlines that are based in third-party countries such as Singapore, Indonesia (not that I'd fly with airlines from that country anyway!) and South Korea.
In general all major airlines will have flight attendants on board that speak at least the following languages :
That's not to say that every flight attendant on the flight will speak all of those languages, but there will be at least one that does. Many airlines have their flight attendants wear pins on their uniform that shows which languages they speak to make it easier to find someone that speaks a specific language.
The languages used for announcements varies depending on the airline and the route, but every flights I've ever been on to Japan has included announcements in both English and Japanese. For flights from South Korea to English speaking countries announcements are made in both Korean and English (Based on flying both Asiana and Korean Air) - I don't know if flights to Japan would include Japanese or not, but I strongly suspect they would.
