This Illumise is a bug-type Pokémon owned by Juliet.
Juliet and Illumise were training with Romeo and Volbeat for the Main Festival. Illumise flew around and used Sweet Scent. However, this caused the leader of the Volbeat, Beat, to be attracted by the scent and mess up, causing everyone to fall in the water. Fortunately, Ash and Brock dived in and rescued everyone. During the night, as Juliet worried what is up with Romeo, a light flashed in the distance. Illumise flew off, but it was a trap, set by Team Rocket. Illumise was captured, which alarmed Juliet to seek help from Romeo and the heroes. Once Team Rocket was found, Beat used Quick Attack, which freed Illumise. Jessie's Seviper attempted to use Poison Tail on the Volbeat, but they were attracted by Illumise's Sweet Scent, causing Seviper to miss. After Team Rocket got defeated, Illumise joined Beat. During that night, Illumise flew in the air during the festival.