If you want a cheap flight from Dundee to Tokyo, you've got one airlines to choose from.
New Tokyo International Airport is just one of the airports in Tokyo. If you're not set on a specific airport, try changing your search from New Tokyo International Airport to Tokyo to see a broader range of flights – they might be cheaper. It usually takes about 25 hrs 30 mins to fly 9203 km to New Tokyo International Airport.
There are about two flights to or via Tokyo every week, so you have plenty of options.
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.