Eiji Saotome, a captain in the Imperial Japanese Army during World War II, founded the Esper Secret Service Corp. His aim was to advocate for Japan's military deployment of esper abilities against the era's major powers. Aware rival nations possessed Level 7 espers, Saotome targeted young adults with high esper levels who faced societal marginalization. With Lord Tsubomi's support, he recruited the youngest members: Level 7 espers Kyousuke Hyoubu and Fujiko Tsubomi. Fujiko Tsubomi persistently distrusted Saotome throughout their association.

As Japan neared defeat under the threat of nuclear strikes, Saotome and higher-ranking officers chose to preserve themselves. They aligned with the foreseen outcome of I-008's vision, which depicted modern Japan thriving under Western victors and Hyoubu descending into terrorism and mass murder. Saotome then betrayed his comrades, shooting Seishiro Uzumi in the back and Hyoubu in the forehead. Uzumi perished; Hyoubu survived. This act culminated Saotome's treachery against the esper unit he established.

Saotome cultivated an image as a loyal, supportive figure, emphasizing esper betterment and welfare to build trust. He exhibited wisdom, intelligence, and rationality, sharing a willingness for extreme measures seen in individuals like Koichi Minamoto. Beneath this persona lay a ruthless, manipulative nature. He viewed espers primarily as expendable assets for his objectives. His gentle, caring demeanor served as a facade for his calculating mindset, enabling him to betray trusting individuals without hesitation when necessary. Fujiko Tsubomi's early suspicions about his true character were ultimately validated by his actions.