Virgil's first Pokémon partner was an Eevee. As a child, Virgil and this Eevee became lost in a forest at night. Their powerful bond, combined with the nocturnal setting, triggered the Eevee's evolution into Umbreon. This newly evolved Umbreon used Flash to light their surroundings and guide them to safety. This pivotal event cemented Virgil's deep appreciation for the Eevee species, ultimately leading him to acquire and train multiple Eevee, each evolved into a different form.

The specific Eevee featured in "Mewtwo ~Kakusei e no Prologue~" remained unevolved. Virgil expressed uncertainty about which evolutionary path this Eevee should follow, setting it apart from his fully evolved team members who had "graduated." Consequently, this Eevee retained its base form while actively participating alongside its evolved counterparts in Virgil's Pokémon Rescue Team operations.

During rescue missions, Eevee proved its utility. In one incident involving Cryogonal attacking a dam, Eevee successfully dug a hole as part of the team's strategy to resolve the situation, showcasing its value despite its unevolved state.

Within the events of the special, Eevee accompanied Virgil during an emergency mountain landing. It joined the subsequent search for an injured Mewtwo, working with Virgil's other Eeveelutions and wild Pokémon summoned by a girl named Anna. Bianca gave Eevee a Casteliacone during this period.

Eevee collaborated with the evolved Eeveelutions during rescue attempts directed at Mewtwo, leveraging the Pokémon team's coordination despite Mewtwo's distrust of humans. These efforts formed part of Virgil's response to the Pokémon hunter Dunc's deceptive scheme to locate Mewtwo.