Yun Arikawa, a 24-year-old engineer and programmer at Otaki Factory, combines technical brilliance with quiet resolve in a small-town robotics workshop. Renowned for crafting intricate robotic systems and writing precise code, he thrives under pressure, his analytical mind outpacing social inclinations. Though introverted, his sharp intuition and bravery emerge during crises, forging strong partnerships with colleagues Haberu Katō and Gorō Ōtaki.

His legacy includes "Naratake," a communication AI that fractured into dual entities: Yung, a stoic smartphone assistant, and Pelops II, a playful canine AI adopted by quantum researcher Mei Kamino. Yung’s fusion with Gorō’s mecha Jet Jaguar granted it autonomous physical form, evolving into the pivotal Jet Jaguar PP—a key weapon against the Catastrophe.

Yun’s investigative genius surfaces in decoding kaiju-linked signals or dissecting abandoned tech, often collaborating with Mei via hurried texts that blend quantum theories and archetype analysis amid kaiju onslaughts. This synergy underscores his knack for merging methodical research with split-second tactical decisions.

His surname—"exist" (有) and "river" (川)—mirrors his adaptive resilience, evident when rerouting Rodan with jury-rigged tech or hacking systems mid-battle against Godzilla. While initially reserved, his bonds with Otaki Factory and Mei trace a subtle arc from solitary technician to indispensable team member, balancing invention with camaraderie.