First mentioned in Volume 14 by Mephisto Pheles and later explained by Ravel, the Rookies Four refers to the four Devils - Sairaorg, Rias, Sona, and Seekvaira as "a generation gathered with promising rookies that are on an exceptional level". Ravel further mentioned that even throughout the history of the Underworld, never before has something like this occurred. She claims that the Rookies Four and their servants belong to something which is out of the ordinary, mostly because they are still starting young Devils who have still yet to mature. Azazel mentions that the reason for the exceptional abilities displayed by the Rookies Four and their servants is due to them doing something that other pure-blooded Devils would not even think to do: training. Majority of the pure-blooded Devils would not train, instead they would only depend solely on the demonic powers that they inherited and would simply trade off any of their servants that they deemed weak. The Rookies Four, however, would rather train their servants instead of making a trade with other Devils.
- Three members of the Rookies Four have had major roles in the story.
- Sairaorg is the only male member of the Rookies Four.
- All members of the Rookies Four have servants that have connections with Dragons.