Description
Sacha journeys to Sinnoh's regional festival to explore its history, reuniting with Dawn and consulting Cynthia for insights into the ancient region. He participates in a catching challenge using replica wooden Poké Balls, temporarily capturing a Rowlet—echoing his past ownership of the species.

His prior Sinnoh experience proves vital when disturbances arise. He instantly coordinates with Dawn and Goh to investigate abnormal Pokémon behavior near Mount Coronet, recognizing connections to past Team Galactic activities involving the Lake Guardians (Azelf, Uxie, and Mesprit), including their previous clash over Dialga and Palkia.

Reuniting with Brock—now training as a Pokémon doctor—Sacha reactivates their historic teamwork. Brock provides logistical support with his medical expertise and evolved Blissey, while Sacha spearheads field operations. Their encounter with Team Galactic commanders Saturn, Mars, and Jupiter reignites their rivalry, the commanders acknowledging Sacha's role in their prior defeat.

Confronting a mutated Heatran empowered by an Arceus Plate, Sacha demonstrates tactical flexibility. He first attempts to cool it with water-type attacks but shifts strategy upon discovering the true Heatran is trapped within the magma shell. He advocates for saving Heatran, persuading Arceus to aid in containment. Sacha then physically enters the magma structure alongside his Pokémon to free Heatran and recover the Plate.

His leadership coordinates allies: directing Dawn, Goh, and Brock during battles against Team Galactic and Heatran, and collaborating with the Lake Guardians. His established bond with Arceus enables their joint effort to stabilize Sinnoh, culminating in a glimpse of Hisui's past that underscores Sacha's place within Sinnoh's history.

Character continuity surfaces through details like his signature high-five with Dawn and Brock's brief return to shirtlessness during the crisis. His temporary capture of Rowlet further reflects his willingness to embrace unconventional methods informed by Sinnoh's history.