If you want a cheap flight from Cardiff to Tokyo, you've got zero airlines to choose from.
Make sure you use the search options above to search for flights to other airports in Tokyo, not just Tokyo Haneda International Airport. The more options you look at, the better your chance of finding a cheap deal.
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.