Hajime Yamaoka

Hajime Yamaoka (山岡 一) was a scientist affiliated with TLT, who died after being used as a hollow shell for Dark Zagi.

Ultraman Nexus
Dated back to 1983, Hajime was a scientist who works for Saijo Chemical Laboratory in Japan. In 1989, he was dispatched to America as part of the Chemical division of US Army Special Forces before he disappeared. In truth, he encountered the wandering spirit of Dark Zagi, who took the man's body as his own and subsequently killed him. Zagi would soon attack the rest of his host's research team in Colorado, sparing a child as part of a bigger plan.

Post morterm
Hajime's body would serve as the vessel of Zagi for years as the dark Ultra erased traces of his former host from the TLT's records to ensure the validity of his disguise.

Trivia

 * According to the final episode of Nexus, Hajime went missing as early as 1989, yet his possession from Dark Zagi happened in 1991 (18 years prior to the series finale). This may be an error of time calculation or his division joined the TLT in said year, making it as a classified information.
 * Judging by the department he previously worked (Saijo Chemical Laboratory), it is possible that Nagi's parents (or an elder relative) are founder/lead figure of it.
 * Since his recorded disappearance was in 1989, it is believed that he was born in circa 1959-1960.