There are three airlines offering flights to Osaka. The most direct route isn’t necessarily the cheapest – being flexible is key to finding the lowest airfare rates. For example, try searching by month to see the best time of the week to fly. The cheapest date is currently 04 / Mar / 2020.
Make sure you use the search options above to search for flights to other airports in Osaka, not just Osaka Kansai International Airport. The more options you look at, the better your chance of finding a cheap deal. Just so you know, the flight typically takes 23 hrs 30 mins.
During this peak season, accommodation prices often increase too, so it's best to book early. Or you could keep your fingers crossed and hold out for a last-minute deal.