Niantic has surprised Pokemon Go players at the anniversary event in Yokohama, Japan with an unannounced Mewtwo raid. Players at the location have begun sharing screenshots of the sudden appearance of the legendary Pokemon, along with a supposed 100 percent catch rate.
Attendees were apparently treated to a QR code when arriving in Yokohama Stadium for the event, but were not told what it was for until they scanned it.
— Nick // Trainer Tips (@trnrtips) August 14, 2017
There is no official information about Mewtwo at the moment, and players are beginning to speculate on when it will appear in other parts of the world. That said, the use of a special promo code may hint that this is going to be a very limited release. At least for the foreseeable future.