Polka Shinoyama, second son of Rozan Shinoyama and one of two heirs to the Shinoyama Financial Group, was born to Rozan and his second wife Kanon Shinoyama. This made him a half-sibling to other Shinoyama family members, a position that fostered resentment among certain relatives. Polka possessed the Elemental Eye, a trait inherited from his mother Kanon, granting him the ability to perceive elemental spirits. Shortly after running away from home, Polka was assassinated by contract killer Misaki Sakimiya, who slit his throat. At the moment of death, an otherworldly necromancer called the Corpse God reincarnated into Polka's body, anchoring Polka's spirit to the physical world. The Corpse God later transferred Polka's spirit into one of Takumi Kuruya's aerial drones. Polka's spirit was subsequently moved again into a stuffed bonito shark toy, which became his permanent form. Polka granted the Corpse God permission to use his identity, and Polka, now inhabiting the shark plush, accompanies the Corpse God. In his original human form, Polka had short white hair and pale blue eyes, typically dressed in casual attire like a light-colored T-shirt and jeans. His reanimated body developed a distinct neck scar and a black lock of bangs after the assassination. As a bonito shark plush, he is small enough to fit in a jacket hood. The toy features visible screws or buttons on its tail and top, along with stitch marks on its snout. Through the Corpse God's magic, the plush moves to express Polka's emotions—smiling or frowning with its mouth and blushing from snout to tail when embarrassed. This specific toy is identified as merchandise from the movie "Sharkborg from Hell (part two)." Relatives described Polka as a "scaredy-cat," exhibiting extreme timidity, particularly around women. This aligned with instances where he blushed intensely when physically close to Misaki Sakimiya. He also displayed visible distress upon suspecting a family member ordered his assassination. Despite his general timidity, Polka demonstrated courage by using his body as a shield to protect others—once as a toddler and again in his shark plush form. His capacity for forgiveness extended even to Misaki, his murderer. Polka's willingness to let the Corpse God assume his identity stemmed from both kindness and practical safety considerations. He expressed genuine enthusiasm for his existence as a shark plush, describing it as "cool" and "swank," and proposed equally outlandish ideas for an android body, like wielding rock drills or flight capabilities. His happiness in this form stems partly from its novelty but also implies he finds it preferable to his previous life, hinting at unresolved familial tensions. His disinterest in wealth further suggested deeper issues within the Shinoyama family. Over time, Polka's experiences as a shark and interactions with the Corpse God's associates—particularly his continued proximity to Misaki—appear to foster personal growth. His embarrassment diminished during subsequent physical contact with Misaki, indicating increased confidence around women. Polka was raised alongside half-siblings who viewed him with varying degrees of acceptance or hostility. His father Rozan remained protective, though Polka's mother Kanon—revealed to be from another world—was largely absent from his life due to trauma-induced amnesia related to her past. The circumstances leading to his running away remain unclear but were likely tied to family dynamics. The full extent of Polka's abilities remains largely unknown beyond his Elemental Eye; no other supernatural or physical capabilities have been documented.