After Genba having successfully activated BoonBoom Safari, Ishiro and Mira pay a visit to an aquarium looking for inspirations to activate BoonBoom Marine, when the Sunseaters return with a fixed-up Boonboom Killer Robo, eager for a rematch.

The Boonboomgers meet Sakito Homura, a mysterious man who possesses the same powers as them, able to transform into Bun Violet and whose intentions are unknown.