Derek Wildstar, born Susumu Kodai, lost his parents in a planetary bombardment that destroyed his hometown. Driven by tragedy, he joined the Earth Defense Force alongside his older brother Mamoru, only to face further loss when Mamoru died in combat—an incident initially attributed to Captain Juzo Okita. Though resentment toward Okita festered early, the captain’s guidance gradually transformed his anger into disciplined resolve.

Once impulsive and emotionally volatile, he matured into leadership roles as tactical officer and acting captain during Okita’s illness. Assuming formal command after Okita’s death, he spearheaded strategic victories against the Comet Empire and interstellar adversaries while overseeing critical missions to stabilize Earth’s dying sun and secure humanity’s future through new colonies.

A proficient pilot, he personally led combat operations with squadrons like the Black Tigers, balancing battlefield daring with collaborative command alongside crewmates such as navigator Mark Venture and radar operator Nova Forrester. His bond with Yuki Mori added personal stakes to his journey, their romance strained by relentless duty and prolonged separations.

Later, he twice deferred command: first to Osamu Yamanami during a time-displacement crisis, then to a resurrected Okita in a climactic battle against existential threats. Retiring to civilian life, he repeatedly returned to service during emergencies, culminating in a final mission aboard a reconstructed spacecraft to confront higher-dimensional forces endangering reality.

His arc centered on reconciling trauma—accepting Okita’s indirect role in his brother’s death and grappling with wartime ethics. Renowned for balancing tactical boldness with empathy, he prioritized civilian protection even in combat. His story closed with a symbolic homecoming to Earth alongside Yuki, aided by interdimensional forces that echoed themes of enduring hope and legacy.