While their jobs are never stated explicitly, it can be assumed that like Shinobu, their works include bodyguarding, gathering intelligence, monitoring enemy forces, manipulating information, subversion, and other dangerous underground activities. Usually they are scattered over the countries doing individual missions.
Although Shinobu is mentioned as the best among them, it is said that each of them has skills close to her. Regardless, all of them respect and value her highly.
Hidden Guards are composed of individuals of varying gender, age, and stature. All of them wear black suit. One of them is visibly carrying a katana strapped at the back.
Second Year Arc
With Shinobu occupied by Tsugumi in battle, Chika Tachibana summoned the rest of Guards in order to capture Marika, who is about to escape from her castle. However, in last second Shinobu herself interfered and switched side, now protecting Marika along with Tsugumi.