Eiryo Ashihana is the puppeteer controlling the automaton Polichinelle and a member of the Assassins Clan. He undertakes contracts primarily for payment, strictly adhering to his professional obligations. His appearance presents a calculated flamboyance: a long dark gray coat over a black button-up shirt, a loose purple tie, white trousers, a yellow belt, shiny dark shoes, and black gloves. Slicked-back hair features slightly wild strands, often accompanied by a smug smile or piercing gaze that reinforces his confident, distant demeanor.

Personality-wise, Eiryo exhibits calm arrogance, displaying pride in his abilities during confrontations like those with Narumi Kato and Shirogane. Though an antagonist, his actions stem from professional logic, not inherent malice. He demonstrates the capacity to respect formidable opponents and reassess situations objectively as events unfold. His complex background reveals he was born into a family renowned for mechanical puppetry, gradually becoming obsessed with developing ever more powerful and lethal automatons. This path led him to embrace the role of a mercenary puppeteer, his expertise making him a significant threat who utilizes Polichinelle to execute contracts efficiently.

Eiryo's development includes moments revealing underlying principles, such as honoring agreements and displaying unexpected depth during interactions with allies or enemies, suggesting motivations beyond financial gain. His involvement in key events, like pursuing Masaru Saiga or clashing with the Shirogane faction, consistently highlights his tactical acumen and combat adaptability. While early portrayals emphasize sadistic tendencies and a power-driven nature, later interactions showcase a more nuanced individual capable of measured decisions, though his core identity as a ruthless professional remains unchanged.