Ensign Kojiro Sakai, a 19-year-old fighter pilot aboard the United Planets Space Force destroyer *Soyokaze*, possesses exceptional skill in spacecraft piloting. He dedicates meticulous daily care to his personal fighter craft, the *Ranpu*, driven by a philosophical pursuit to merge with the machine as an extension of his own body.

Sakai exhibits gynophobia—a pronounced fear of women frequently misinterpreted as misogyny—manifesting in aggressive or avoidant reactions to female physical proximity, particularly near his aircraft. Despite this aversion, he volunteers to train twins Emi and Yumi Hanner upon recognizing their innate piloting abilities exceed standard metrics. Their persistent presence tests his discomfort, yet they grow to respect his expertise.

His personality combines intense volatility and defensiveness, especially concerning the *Ranpu*. He forbids others from touching it and reacts combatively to perceived intrusions, fueling frequent clashes with the *Soyokaze*’s Marines, notably their leader Mickey Cryburn. Though these conflicts imply rivalry, Sakai demonstrates cooperative capacity during critical missions, revealing underlying camaraderie beneath surface antagonism.

Post-service, Sakai resides in a United Planets Space Force retirement home. He spends his later years recounting military experiences, blending factual events with embellishment, understatement, or conflation.