Cicada season in Japan, like North America, seems to be best from June to September, peaking in August. Different cicada species emerge at different times of the year, but the majority of them are active during the summer.
Cicadas are very popular in Japan, and they find their way into pop culture (Anime, live action kids shows like Ultraman). This photo features a cicada toy when spun, makes a sound, some cicada clicker toys, a plush Oncotympana, a Seminingen (bad guy from Ultraman), and Yotsuba a green-haired girl who has caught a cicada (Lyristes japonicus perhaps):
Cicada News & Photos
The best place, I’ve found, to keep track of which cicadas are out in Japan is Twitter. You can search Twitter yourself for ã‚»ãƒŸ and you’ll find many results — most Tweets are references to pop culture, but occasional photos and actual information about actual cicadas.
These are many of the Twitter feeds I follow. You don’t need to belong to Twitter to view their feeds, but it’s more fun if you join.