Hyakume operates as the radar and sensor expert aboard the pirate vessel Bentenmaru, tasked with tracking enemy ships, identifying spatial anomalies, and directing electronic warfare systems during missions. His appearance includes dark brown hair with a slight mustache and beard, a gaunt face, and a scar above his left eye, typically paired with a tilted red headband, a light blue scarf, and maroon fingerless gloves. In the manga, his design changes to light grey hair hidden under a bandana and a dark suit with a blue jacket featuring circular indentations. He maintains a friendly, often amused disposition, regularly offering technical explanations or speculative theories mid-operation.

No prior background exists before his Bentenmaru service. His technical skills prove vital across multiple events: during Marika Kato’s training, he monitors the yacht Odette II’s sensor data and oversees her electronic warfare drills. In the Golden Ghost Ship incident, he detects energy surges from the Serenity Corback, records combat data through enemy jamming, and helps breach secured networks to locate spatial distortions before joining the boarding party to analyze the ghost ship’s electronic and environmental systems. When the Hakuoh Pirates arc unfolds, he co-authors an emergency manual during the core crew’s quarantine, reacts with visible alarm to operational errors like misfired cannons, and later reads news reports about Hakuoh Academy’s pirate raid. Off-duty, he assembles model ships—sometimes collapsing mid-build—and plays cards with crewmates, displaying concern for Marika’s welfare during their isolation.