If you want a cheap flight from Lisbon to Tokyo, you've got 15 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 24 hrs 5 mins to fly 11164 km to New Tokyo International Airport.
58 flights go to or via Tokyo every week. The most popular airline is Etihad Airways but do spend some time checking all your options – they aren’t necessarily the cheapest airline to book with.
If you're planning on going to Tokyo during this time, you could take a look at other airport options. Or you could try to get a last-minute bargain.