Office of Secret Intelligence

The Office of Secret Intelligence is an intelligence agency answerable only to the Emperor, tasked, among other tasks befitting a secret agency, with the capture of C.C. Its members appear not to have been informed of C.C.'s immortality, and only a few selected agents have been disclosed to the true power of Geass.

Organization History
The Agency in 2018 was tasked by the Emperor to monitor Lelouch and to search for the whereabouts of C.C. After the tampering of Lelouch's memory by Emperor Charles, Lelouch is kept under constant surveillance without him ever noticing, a testament to their secretive nature. The Agency also kept tab of every one Lelouch's activities whether it's waking up in the morning to skipping classes and they kept the detailed information inside a journal, which one Agent of the OSI described as a "Breeding Log" and regarded Lelouch as nothing more than "bait" or a "trap" to capture C.C.

The OSI Base is secretly hidden inside Ashford Academy, the entrance to the OSI is located behind a bookshelf. The bookshelf is a disguised door to an elevator that goes underground, where headquarters of the OSI is located. Most Agents of the OSI are well disguised as teachers or as members of the school staff and some are disguised as a civilians, but some OSI members can also be seen in which can be safely assumed as their uniform.

Under the leadership of Villetta Nu, the OSI was tasked to monitor Lelouch's activity and captured C.C. for the Emperor, but after she restores his memory and his Geass power, Lelouch manages to infiltrate the headquarters and also persuaded Rolo to join his side. With Rolo's help, Lelouch successfully blackmailed Villetta in exchange for his silence. From then on Villetta is forced to serve him and he also Geassed several other members. Because of this Lelouch now had the entire OSI in his command. After Lelouch's ascension to the throne it is not revealed what happened to the OSI.

Under the Emperor's Command
While the OSI is still a government organization, their agency is not tied down by bureaucracy and they only take orders directly from the Emperor. While operating they are granted a "Carte Blanche" to do whatever they want, from disregarding a common protocol to mass murder. While chasing Lelouch inside the Babel Tower, the OSI field agents murdered innocent civilians in cold blood and used flamethrowers to dispose the bodies.