Kouichi Tsuruuchi, a senior Garde pilot and former Samari squad member, balances a carefree, irreverent attitude with sharp combat focus. Now leading his own unit, he playfully flirts with commanding officer Samari Ittan, though she repeatedly rejects his advances. Off-duty humor gives way to battlefield discipline, where his tactical prowess shines. Notorious for reckless reliance on heavy weapons like the Heigus Cannon, he remains lethally efficient in critical missions. He fights in critical engagements such as repelling Gauna 487, rescuing Nagate Tanikaze and Shizuka Hoshijiro, and assaulting the Large Mass Union ship. During the latter, he expends all Heigus Particles in a daring gambit to breach a Gauna pod’s core, abandoning retreat until later rescue. Against Chimera Ochiai, he survives a near-fatal suicidal strike, enduring lengthy recovery. His comedic pursuit of Samari—including cheeky proposals to “photosynthesize” together, alluding to Sidonia’s bioengineered physiology—persists in public interactions and squad photos. Tsuruuchi’s rugged features—blonde swept-back hair, a prominent nose, and piercing blue eyes—contrast with standard Garde uniform practicality. His call number 007 denotes seventh-ranked seniority. Though bravado veils moments of doubt, like after the Akai squad’s defeat by Gauna 487, his unyielding courage and loyalty cement his role as Sidonia’s irreverent yet indispensable protector.