Sacha, accompanied by Pikachu and companions Serena, Clemont, and Bonnie, journeys to a desert city by the sea. During their travels, they encounter the Mythical Pokémon Hoopa, who uses its interdimensional rings to teleport them instantly to Dahara City. This marks Sacha's first encounter with Hoopa, whose playful nature initially reveals itself through tricks like attempting to steal donuts. Sacha learns of Hoopa's past, including its destructive rampage a century earlier that forced the sealing of its power within the Prison Bottle. When this bottle shatters, Hoopa's uncontrolled power manifests as a separate entity, Hoopa Unbound. This form unleashes chaos, summoning legendary Pokémon—Primal Groudon, Primal Kyogre, Dialga, Palkia, Giratina, and Kyurem—to attack Dahara City. In response, Sacha aids Hoopa in summoning its own allies: Lugia, Latios, Latias, and a Shiny Mega Rayquaza, to counter the threat. During the climactic battle above the city, Sacha actively participates, commanding Rayquaza, Latias, and Latios against the opposing legendary Pokémon. He rides Latias alongside Hoopa and Pikachu to engage directly in the conflict. Simultaneously, Sacha supports efforts to recreate the Prison Bottle, which requires harnessing elemental energies from Serena's Braixen (fire), his Frogadier (water), and a wild Hippopotas (earth). This new bottle is essential for containing Hoopa's rampaging power. At a critical moment, Sacha catches the newly forged Prison Bottle and becomes temporarily possessed by the malevolent force of Hoopa Unbound. He is freed when Hoopa uses its positive memories to purify the shadow entity. Following Hoopa Unbound's defeat, a spacetime rift threatens the city. Sacha and the others evacuate using Hoopa's rings, with Arceus intervening to stabilize the rift, allowing Hoopa to escape safely. Hoopa chooses to remain with its caretakers, Baraz and Meray, to help rebuild Dahara City.