Kōichi Tsurūchi is the senior Garde pilot of Sidonia's Samari squad, designated unit 007. He possesses an easy-going and frequently irreverent personality, often directing rude jokes at his commanding officer, Samari Ittan. This includes repeated, unsuccessful romantic advances toward her, comically rebuffed—like being elbowed away in group photos. Despite his off-duty levity, Tsurūchi displays significant skill and combat-ready focus during operations. He participates in critical battles defending against Gauna 487 and rescuing Nagate Tanikaze and Shizuka Hoshijiro. During the engagement with the Large Mass Union ship, he acts nobly, sacrificing his return trajectory to destroy a Gauna pod. He expends his Garde's entire Heigus Particle reserve to breach the pod's core, necessitating rescue by Ichirou Seii. His combat style proves formidable but sometimes reckless, marked by overreliance on the Heigus Cannon. Tsurūchi nearly dies confronting Chimera Ochiai, intentionally sacrificing his Garde unit to eliminate the threat. Severely injured, he survives via escape pod ejection and makes a full recovery. Outside piloting, he competes in Sidonia's Gravity Festival against Kashiwade Aoki, only to be knocked out of the arena and defeated. Physically, Tsurūchi has blonde hair combed backward, blue eyes, and a prominent nose. His behavior contributes to him often being cited as one of the less conventionally attractive pilots. His call sign, 007, confirms his rank as the seventh Garde pilot.