Yamaneko Arthur is one of six warriors chosen by the sacred sword Excalibur. Designated as the group's sniper, her mission focuses on restoring the world's distorted history by defeating those who abuse Excalibur's power, specifically requiring travel to England to confront individuals threatening historical integrity.

Initially appearing unsociable, she wields the Magic Cannon, a rocket launcher firing elemental projectiles. These projectiles—fire, ice, wind, and void—produce distinct effects like wall bounces, freezing, or extended hit stun depending on the element and charge level. Her combat style emphasizes zoning and projectile control, leveraging these elemental properties to dominate opponents at range.

Beneath her reserved exterior lies a more complex personality. She exhibits significant shyness, blushing easily when receiving compliments or physical contact from the group's leader, Dancho Arthur. Protective instincts surface strongly towards Dancho, including physically defending him and accepting his playful traps over alternatives. She demonstrates care for teammates, rescuing Arthur Aqua by holding her waist and persistently searching for Utahime during a competition to protect her from a threat. She also indirectly supports teammates Tekken and Kakka by shyly endorsing their romantic pairing.

Her development reveals moments of heightened emotion contrasting her usual reticence: panic encountering Utahime in competitions, excitement when Dancho compliments her swimsuit. These moments indicate growing comfort within the team.

Physically, she possesses purple hair reaching her chest and blue eyes, presenting a teenage appearance. No details about her origin or life before the mission are provided.