Colonel Ryū Yamaki commands the Galactic Federal Army's Intelligence Division as its Director General, spearheading operations to neutralize Lady Kahn's escalating threat. Charged with recruiting the formidable esper Locke from his self-imposed pastoral exile, Yamaki persists through initial rejections until securing the recluse's reluctant partnership. He orchestrates counterintelligence strategies against Kahn's army of engineered espers, unaware her most lethal weapon—brainwashed assassin Jessica—infiltrates his ranks under fabricated amnesia. Jessica's manufactured bond with Yamaki fractures when recovered memories of her parents' alleged murder by Locke ignite vengeful hostilities.

Functioning as both liaison and logistical anchor between Locke and the Federation, Yamaki cultivates tactical rapport through shared routines in Locke's rustic world. Their exchanges balance military pragmatism with mutual respect, threading strategic dialogue through sheepfold chores. While his unwavering duty to galactic stability defines his command presence, the origins and private drives fueling his service remain guarded, leaving the disciplined colonel an enigma wrapped in uniformed authority.