Akimu Papladon is a character who undergoes a dramatic transformation, originating as a demon named Pantomime before being resurrected as the artificial demon designated as No. 9. In his first life as Pantomime, he was a servant to the demon king Wolf Daddy. He possessed a lighthearted and childish demeanor, especially when using his natural talent for imitating the magical abilities of other demons through touch. His mission was to travel to the human world, but he was killed by Braz Blood before he could complete it. The portal he had opened, however, remained, inadvertently bringing the human girl Fuyumi Yanagi into the demon world.

Following his death, Braz delivered Pantomime's body to the scientist Franken Stein for experimentation. Stein resurrected the demon, creating a new being with no memories of his past life, and gave him the name Akimu Papladon. As Akimu, his personality is a stark contrast to his former self. He becomes utterly obsessed with gaining power and growing stronger, believing his own body to be inherently weak. To remedy this, he embarks on a relentless quest to collect the strongest body parts from other demons, forcibly taking them and stitching them onto his own form. This gives him a constantly changing, patchwork appearance marked by numerous scars and stitches. His hair is typically white with darker bangs, and his eyes are a pale yellow. His composite body includes features like a longer, fur-covered arm taken from an ape-like demon, and a large seam across his chest that can open into a maw of sharp teeth to consume his opponents. He is arrogant, confident, and holds himself above others, viewing himself as an apex predator. He finds a twisted sense of beauty in powerful and efficient fighting techniques, often complimenting his enemies on their skills, but he is also unabashedly cruel, sadistic, and finds amusement in the terror he causes. Despite his monstrous demeanor, he proves to be cunning and intelligent, often outwitting even his creators.

Akimu serves as a major antagonist, his role centered on his single-minded pursuit of power. After escaping from Franken Stein's laboratory using spatial magic, he goes on a rampage across the demon world, hunting for body parts. His conflict with the series protagonist, Staz Charlie Blood, begins when Staz defeats him as part of a deal to learn how to resurrect humans. Even in defeat, Akimu is resourceful. Though his body is severed into pieces by Bell Hydra, his consciousness as a phantom presence allows him to survive. He is later placed in a new body—that of Richarz Blood—to be used as a power source, but his own magic eventually reanimates his original form. He outsmarts Franken to retrieve his heart from Richarz, killing him in the process, and then destroys the Door of Magical Essence. After absorbing the released magic, he proclaims himself the King of the Demon World Acropolis.

Akimu's key relationships are largely antagonistic or instrumental. He is a creation of Franken Stein, whom he eventually betrays. He is a tool in the schemes of Braz Blood, who intends to use him to overthrow King Wolf. His primary rival is Staz, who defeats him and stands as an obstacle to his ambitions. His body parts are sought after by Bell Hydra, who possesses the original spatial magic that Akimu only imitates.

His development is a tragic or horrific arc from a simple, obedient, and cheerful servant into a power-hungry, sadistic, and independent artificial monster. His initial motivation was simply to follow orders, but as Akimu, his sole driving force becomes the acquisition of strength for its own sake. He evolves from being a pawn in others' political games into a self-proclaimed king and a significant, independent threat to the entire demon world.

Akimu possesses several notable abilities. As a phantom presence, his physical body is merely a vessel he manipulates with his magic, making him incredibly resilient; even severed limbs or a broken arm can still be controlled, and he can reattach his parts. His original ability, which he retains, is imitation magic, allowing him to copy the powers of other demons. He also wields imitation spatial magic, which he stole from the Hydra family, enabling him to create portals to travel anywhere. After absorbing Richarz Blood's powers, he gains the terrifying ability to absorb the magic of other demons on contact, using it to strengthen himself. He can also use this absorbed magic to reanimate and control corpses, turning them into his own artificial demon army. His power level, measured in "organs," grows immensely over the course of the story, eventually reaching astronomical numbers as he continues to absorb more and more power.