Eiji Arashiba leads Helios, the Akatsuki Special Zone's troubleshooter organization, renowned as the "Hero of Akatsuki" for safeguarding the zone after it fell into lawlessness during the Akatsuki Rebellion four years ago. He stands tall and slender, a young man with striking blue eyes and brown hair falling to his neck.

His everyday demeanor is typically aloof, yet he reveals fierce loyalty and formidable protective instincts when defending friends or the community. Eiji holds the manager title at the book café Titan, though daily operations rest primarily with his brother, Kazuma Arashiba. Kazuma frequently admonishes Eiji for neglecting these duties, yet Eiji seems to find a quiet contentment in their relationship, including his brother's scolding.

Eiji once bore the Cerberus tattoo, a Scard granting him immunity to physical harm and the ability to detect an opponent's killing intent, the "smell of murder." This power was central to his effectiveness as a protector. He later chose to relinquish the Cerberus tattoo, transferring it to Yamato Kai. In combat, Eiji employs firearms, often wielding dual pistols, confronting threats directly to maintain order within Akatsuki's lawless environment.