Kiwi.com is one of the best sites to use when searching for flights.
The prices are so much better than what you'll find on SkyScanner / sometimes your own travel agent
You can also see other locations around the world for the dates you are searching for.
Zoom in and you'll see more destinations with a price tag hovering above each city name :)
If you are going to Tokyo this year in July/August
Make sure to head south to Kyoto, Osaka, and more places
for very many amazing festivals that will be happening in the summer months. ^_^