Riku Heisenberg commands the Black Gema Gema Corps as its marshal, opposing protagonists like Dejiko while simultaneously working as a veterinarian. His deep fondness for animals manifests through frequent appearances with various creatures perched on his shoulders. Physically tall with light purple hair and dark brown or red eyes, he wears glasses and a tie with his uniform. His design incorporates animal traits: dog ears, a tail, and a collar.

Beneath a serious, composed exterior lies a sillier, lighthearted personality, making him a humorous figure within the group. His unwavering loyalty to the King and Queen of Planet Analogue fuels persistent participation in the Corps' schemes. He adopts a paternal role among members, particularly toward Piyoko, who calls him "Daddy."

His narrative arc begins in the *Di Gi Charat Christmas Special*, establishing his role and paternal dynamic with Piyoko—later revisited in *A Trip to the Planet*. During that story, he attempts to sabotage Dejiko's journey, even disguising himself as an elderly woman to deliver sedative-laced food. He also features in the special *Kuchi Kara Bazooka*, collaborating to amplify Piyoko’s "Mouth Bazooka" ability against Dejiko’s attacks, reinforcing his supportive function.

His dedication stems from service to Planet Analogue’s rulers, driving the Corps' recurring objective: kidnapping Dejiko for ransom to aid their home planet.