Kasumi, internationally known as Misty, journeys alongside Ash Ketchum and Brock to Arborville in the Johto region. Upon arrival, she witnesses the legendary Pokémon Suicune on a riverbank. Alongside her companions, she learns of the "Voice of the Forest" from Towa and her granddaughter, Diana. Exploring the forest, Kasumi encounters Sammy, a boy displaced 40 years from the past, and the mythical Pokémon Celebi. She helps locate the injured Celebi and assists in transporting it to the Lake of Life for healing. Fleeing the antagonist, the Iron Masked Marauder, she suffers a knee injury. Brock carries her during their escape, and her injury heals in the Lake of Life's restorative waters. Kasumi witnesses the Iron Masked Marauder capture Celebi using a Dark Ball, which corrupts the Pokémon and amplifies its powers. She observes Celebi morph into a destructive, plant-based entity under the Marauder's control. Following the climactic battle where Ash and Sammy free Celebi, Kasumi is present when Celebi collapses and appears to die. She then sees other Celebi arrive from different timelines to revive it. After Celebi's revival and Sammy's return to his own time, Kasumi departs Arborville with Ash and Brock. She participates in recounting their adventure to Professor Oak and expresses surprise when he demonstrates prior knowledge of Sammy's name, despite them never mentioning it during their call.