Voiced by: Motomu Kiyokawa (Japanese), Guil Lunde, (TV) Michael Ross, (film) Kent Williams (Rebuild) (English)
Kozo Fuyutsuki (冬月 コウゾウ, Fuyutsuki Kōzō?) is Nerv's Deputy Commander and Gendo Ikari's right hand man. He does not especially like Gendo, but he is the closest thing to a confidant that Gendo has in the series.
Once a professor of meta-biology at Kyoto University, Fuyutsuki became interested in the research and theories undertaken by Yui Ikari, and became her sponsor and mentor. Shortly thereafter, he was directed by his superiors to initiate a similar arrangement with Gendo Rokobungi. Later, after the Second Impact, Fuyutsuki traveled with Gendo to the ruins of Antarctica, and began to suspect that Gendo and his associates in Seele were more powerful and dangerous than he originally realized. In 2003, Fuyutsuki discovered for himself the true nature of the events leading up to Second Impact and Seele's involvement in initiating that catastrophe. Gendo led him into the GeoFront and Central Dogma, and asked Fuyutsuki to join him in "creating a new future for mankind."
During a flashback scene in The End of Evangelion, Fuyutsuki mentions that Seele had threatened to make him "disappear", implying that his recruitment may have been extortionary. Although Fuyutsuki was never more than a mentor and friend to Yui, it is implied that he was in love with her to some degree, as he was shocked to learn that she was marrying Gendo. In The End of Evangelion Lilith/Rei takes the form of Yui to achieve Fuyutsuki's Instrumentality.