Nerv Department of Security Intelligence
The Nerv Department of Security Intelligence is the subsection of Nerv which, apart from their intelligence-gathering and counter-intelligence activities, includes special agents who follow around Evangelion pilots and investigate security breaches. In Episode 04, they were able to retrieve Shinji Ikari after he ran away from Misato for nearly two days. They also confronted Misato Katsuragi in Episode 21 when Ryoji Kaji kidnapped Kozo Fuyutsuki, and also rescued Asuka Langley Soryu from an apparent suicide attempt after she ran away from Hikari Horaki in Episode 24.
It is implied that their allegiance is not entirely to Nerv, since they can be capable of incredible lapses of security when needed, such as allowing Fuyutsuki's kidnapping to take place and losing track of Asuka for a week and reacquiring her on the same day that Kaworu arrived as a replacement pilot. However, the exact scope of their involvement in events such as Kaji's murder (and possibly even the Episode 11 blackout and the JSSDF invasion in End of Evangelion) remains purely speculative.
The Department of Security Intelligence is also popularly known by some fans as "Section Two" or "Second Section"; agents working within that department are referred to as the "Men in Black" due to their identical black three-piece suits.
|"The Men in Black"|