Akira Yanagida is a First Lieutenant in the Japan Ground Self-Defense Force and serves as an acquaintance and occasional foil to protagonist Yōji Itami. A graduate of the National Defense Academy of Japan with high honors, Yanagida is a career officer who prides himself on his elite educational background, though he carries a lingering sense of inferiority stemming from having failed to gain admission to Tokyo University.

In terms of appearance, Yanagida is a tall, handsome man with short black hair parted on the left side, who almost always wears glasses and a formal military uniform. His typical expression is a wide grin, which complements his often mischievous and sly demeanor. He is frequently seen smoking, particularly during conversations with Itami.

Yanagida's personality is complex, blending sharp intellect with a noticeable streak of envy and arrogance. He is a calm, analytical, and politically savvy officer who functions effectively as an adjutant to Lieutenant General Kōichirō Hazama, demonstrating a strong understanding of logistics, administration, and the bureaucratic aspects of military operations. Despite his professional competence, he is prone to stress-induced impetuousness and can lose his cool in a comical fashion, such as when he performed a curse ritual outside Itami's office upon discovering his own stress-related hair loss, hoping Itami would go bald as well.

His relationship with Yōji Itami is central to his character. Yanagida frequently annoys and makes sarcastic remarks toward Itami, driven by a deep-seated jealousy over Itami's rapid promotion following the Ginza Incident. Yanagida resents that Itami, who he believes joined the military merely to support his hobbies, advanced through luck while Yanagida himself struggled to achieve the same rank. During the mission to slay the Flame Dragon, Yanagida openly expressed his hatred for Itami under the stress of the situation, though he later apologized, and Itami did not take the outburst personally. Despite this rivalry, Yanagida is consistently willing to defend Itami's questionable actions to superior officers, arguing that Itami's methods benefit Japan by securing resources and strategic advantages. He also quietly supports Itami by arranging supplies and minimizing bureaucratic fallout, and he expresses genuine envy for Itami's unique ability to inspire loyalty and attract followers naturally.

Yanagida's most significant action in the field occurs when he intervenes to protect Noriko Mochizuki from an assassination attempt by Delilah, a warrior from the Rabbit Tribe. Despite being primarily an administrative officer with limited frontline combat training, Yanagida confronted the physically superior Delilah. He was stabbed in the abdomen but managed to shoot her at point-blank range, resulting in both being severely wounded and losing consciousness. Both survived, though Yanagida was left with permanent physical handicaps as a result of his injuries. This act of bravery, undertaken at great personal risk, forms the foundation of his later relationship with Delilah, who becomes his devoted partner and personal warrior, assisting him with daily life and missions.

Yanagida's development sees him move from a somewhat antagonistic, envious rival to a grudgingly respected and loyal ally. He is described by Princess Piña Co Lada as a snake-like and unpleasant man, and Bozes Co Palesti considers him even more arrogant than General Hazama. However, his actions consistently reveal a strong sense of duty, patriotism, and a willingness to shoulder burdens for the sake of his comrades and national interest. During the crisis of the Gate's closure, he leads a successful extraction operation, securing the escape of key individuals to Japan. Following the Gate's closing, he remains in the JSDF, continues his relationship with Delilah, and maintains close ties with former members of the Third Reconnaissance Team.

His notable abilities lie not in direct combat prowess but in strategic planning, logistics, intelligence coordination, and political maneuvering. He is an excellent administrator and a natural strategist who excels at getting things done efficiently behind the scenes. Despite his lack of frontline experience, his confrontation with Delilah demonstrates that he possesses considerable courage and adaptability under extreme pressure.