Once a professor of meta-biology at Kyoto University, Kohzou Fuyutsuki now serves as the Deputy Commander of NERV under Gendo. Despite his authoritative demeanor and apparent ease in command, he is not a military man. The director's cut reveals that he has some medical training but lacks or never acquired a license to practice medicine. Throughout the series, there are no indications of romantic relationships or dependents.
In "The Birth of NERV" episode, flashbacks show several students and a superior professor at his institute suggesting he be more sociable, hinting at Fuyutsuki being a classically withdrawn academic, possibly a lifelong bachelor. Shortly after beginning an academic relationship with Yui Ikari, which was both platonically affectionate and supportive, his institution's superiors directed him to initiate a similar arrangement with then-Gendo Rokobungi.
Considering SEELE's decades-long machinations into Instrumentality-related sciences, it is plausible that Professor Fuyutsuki was monitored by and targeted for recruitment early in his career. If speculations about Yui being a junior member of SEELE through her father's influence are correct, Fuyutsuki's association with Gendo Rokobungi/Ikari was equally pre-planned. His introduction to Rokobungi/Ikari, including bailing him out of jail and meeting again post-Second Impact during an Antarctic research expedition, might have been steps in testing his reliability, discretion, and intelligence regarding SEELE’s goals.
Fuyutsuki's initial assessment of Gendo Ikari's personality, reinforced during the Antarctic mission, led him to suspect that Gendo's associates in SEELE were more powerful and dangerous than initially realized. This doubt culminated in discovering SEELE's involvement in initiating Second Impact. After threatening to expose Gendo concerning the deception around Second Impact, Gendo revealed an incomplete prototype Eva to Fuyutsuki, inviting him to join and create a new future for humankind. Whether this agreement stemmed from idealism or self-preservation remains unclear. In "The End of Evangelion," it is mentioned that SEELE had threatened Fuyutsuki with disappearance, implying his recruitment may have been a Hobson's choice.
Despite initial dislike, Fuyutsuki becomes Gendo's closest confidant. He often acts as an external conscience for Gendo, genuinely concerned for those under his command while balancing compassion with Ikari's ruthlessness in pursuing SEELE's agenda and his hidden one of reuniting with Yui. Gendo's dependence on Fuyutsuki is evident in numerous instances where Fuyutsuki takes initiative without waiting for direction.
While kindly disposed towards Yui, Fuyutsuki maintained a professional demeanor towards her. The impact of the Destrudo experiment that 'killed' her and ensconced her soul into EVA Unit 01 on him is not clear. However, the depth of his feelings for her is revealed when, prior to dematerializing into LCL during Instrumentality, he witnesses an image of Lilith-as-Yui floating down to embrace him, comforting him in his transition to a non-corporeal state.
