Aizu Yudagawa serves as a Kildren fighter pilot at Area 262 under commanding officer Suito Kusanagi. Genetically engineered for eternal adolescence, he lives a cyclical existence defined by combat missions and base life. He possesses distinctive white hair and grey eyes, typically seen in a standard pilot's jacket.

His reserved and introverted personality contrasts with more sociable squadron members like Naofumi Tokino. Yudagawa prefers solitude and silence, often observed reading a newspaper during downtime. After finishing, he meticulously folds the paper in a precise, neurotic routine noted by others. He voluntarily associates primarily with fellow pilot Uroyuki Shinoda, who respects his preference for minimal conversation.

Despite his introverted nature, Yudagawa demonstrates professionalism in combat. He occasionally assumes command responsibilities during Kusanagi's absences, indicating leadership trust. During a critical sortie, he spots enemy bombers escorted by fighters. Disregarding coordination, he impulsively dives ahead to engage alone and is shot down and killed by the enemy ace known as "The Teacher," his plane sinking into the ocean.

Following his death, a new pilot named Aihara arrives at Area 262. Aihara bears an identical physical appearance to Yudagawa and exhibits the same distinctive newspaper-folding habit. This replacement underscores the Kildren's cyclical existence, where fallen pilots are seemingly regenerated or replaced, perpetuating their unchanging roles in the war.