Sakimori is one of the few PPC agents who is also a canonical character, albeit a bit part. In Chapter 10 of the Digimon NEXT manga, a Commandramon—a Rookie-level Digimon serving as a grunt in the Big Bad's army—who had been damaged was shot for being "useless," and toppled into the literal firewall surrounding the Big Bad's fortress. It was believed he burned up.
What happened after that has been pieced together from testimony and logical continuation. The Commandramon, more dead than alive, fell through a plothole (as nothing else ever came in contact with that firewall) and landed in the Avatar: The Last Airbender continuum. There, by a combination of the best and worst luck imaginable, he came into contact with a Mary Sue and was transformed into her Cute Animal Friend—a blue dragon.
When Technicians Narcolepsy and James Fairchild killed the Sue for the purpose of stealing her gizmos, they were quite surprised to find her CAF transforming into a four-foot dinosaur in body armor who seemed to be fading in and out of existence. After hauling him back to their lab and running basic diagnostics, they determined where he was from and that he couldn't exactly go back. Thus, they turned him over to Medical—and from Medical, to Personnel.
The same bright spark in Personnel who named his future partner, presumably, got the idea of giving this Commandramon his name—since just calling him by his species, as Digimon usually are, would get confusing if there were ever more than one around. That Personnel clerk dubbed the new agent "Sakimori," literally "border guard," and sent him off.
Sakimori stands roughly four feet high, as his normally hunched saurian posture was somewhat straightened by his stint as a dragon. He has blue-and-white camouflage-patterned skin and gold, reptilian eyes, and wears a multipiece suit of body armor effectively constantly. He weighs more than you'd expect.
Sakimori's body armor is technically removable, but it is also technically part of him, and cannot be taken off without considerable effort and causing some level of discomfort to him both in the removal and in having it off. As such, he tends to keep it on at all times. The same is true of his weapon, though to a lesser extent.
When in disguise, Sakimori tends to keep his helmet if at all possible; his haircut defaults to a GI buzz that is wholly unflattering. His disguise maintains one obvious tell: his eyes are always gold, with reptilian pupils.
Sakimori is the ideal military 'Mon: diligent, attentive, respectful, and eager to follow orders. At the same time, however, his experience and training make him the more level-headed of his partnership, meaning that he often has to act as Rococo's "handler," keeping him from charging headfirst into dangerous situations, acting before the time is right, or just acting like an idiot in general.
Nevertheless, Sakimori adores his partner, and will stand by his side in thick or thin—just as any Digimon with a partner would—and as such tends to find himself hauled into dangerous situations. Fortunately, he has the experience to handle them, and is extremely cool under fire—though he has shown a worrying tendency to break the Military Man veneer at times and go bomb-happy. He is an ex-Evil Mook, after all.
Additionally, Sakimori has been finding it hard to adjust to the strongly individualistic PPC after having spent his whole life as a line-grunt in a faceless organization, to say nothing of being a member of a species that typically doesn't give its individual members their own names. The culture shock is a bit terrifying at times, and he's certainly not used to the recognition.
It is possible for Sakimori to change the color and pattern of his skin and armor, thus camouflaging himself like a chameleon, but he has never been trained in doing so and may not yet even know it is possible himself.