Pokémon GO Wild Area: Sendai • Tohoku will introduce a first-come, first-served ticket registration process, with Trainers able to register their interest beginning Sept. 11 at 8 a.m. JST through the official Pokémon GO website. Registration will remain open until Sept. 15 at 7:59 a.m. JST and will not require payment, but tickets are limited and availability is not guaranteed for everyone who registers. After registration closes, requests will be processed in the order they were received, with successful Trainers notified through in-game News and given a dedicated window to purchase tickets, with a maximum of four tickets allowed per order. Add-ons such as Extra Day options can be purchased after securing tickets, although a specific event date is not guaranteed. The new registration system applies only to Pokémon GO Wild Area: Sendai • Tohoku, while tickets for the global and Mexico City Wild Area events will remain unaffected and go on sale separately.
Source: Official Pokémon GO blog