To tie in with Pokémon the Movie: I Choose You!, the repeat of the first special promotion has kicked off for Pokémon Sun and Moon players in Japan. If you had previously prebooked tickets in Japan, you would have received get a serial code that can be used to unlock one of six Pikachu wearing one of Ash’s caps from over the years. This distribution provides Original Cap Pikachu, which features Ash’s hat from the Kanto and Johto series of the Pokémon anime. This Pikachu also comes with the special Pikashunium Z Z-Crystal, which turns the move Thunderbolt into the Z-Move 10,000,000 Volt Thunderbolt. This distribution is available until July 31, 2017, and is the last chance to get this cap of Pikachu in Japan. No international distributions have been announced as yet, but stay tuned for any updates.
Source: Serebii
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