The ability to summon a Persona or make use of a Shadow is not the only benefit these people may possess. Called resonance, it is a sort of sixth sense that can be parsed in a number of ways by other Persona-users or Shadow-Possessed... or not, sometimes, as the case may be. In some cases, even civilians can glean a bit of this sense from a Shadow-Possessed or Persona-user, but it isn't common. Some Shadow-Possessed or Persona-users gain additional powers from their understanding and manipulation of their resonance; these are all covered under Support Persona.
This file intends to address the nature of resonance, how it can be detected, and how it can be concealed.
Resonance at its most basic level is a marker of a person or being that possesses supernatural powers. Civilians do not possess any resonance whatsoever. While demons and Shadows possess resonance, though, theirs cannot be detected by anyone other that those characters discussed in Support Persona. It's much easier, but by no means a certain thing, between Shadow-Possessed or Persona-users, as the Shadows or Personas call out to one another. It comes in a variety of ways, and is typically felt to fall under the broad 'five senses' by those detecting it.
Detecting and Hiding Resonance
Detecting resonance is easy. The character receives a vague feeling, often colored by one of the five senses, of some aspect of the character's resonance. For example, a character who describes their resonance as feeling like 'a lamp at night' may give the impression of brightness, or may smell like ozone or night air. The possibilities are endless.
For most Persona-users or Shadow-Possessed, this is merely the vague knowledge or feeling that a presence is very close by; unless the target is well and truly alone, it can be difficult to pinpoint, and even then, unless the user is a very talented "spotter" or the target is a very strong Persona-user, it can be missed. Two average Persona-users or Shadow-Possessed will quite likely not notice one another in the least.
There are factors that make sensing a target easier, of course. The more immediately dangerous a situation is, the more likely one is to sense something; one's sixth sense, like the other five, is more acute in the face of known imminent danger. The more intimately one knows the target, the more likely one is to sense a resonance; as a result, one often needs to know at least a modest amount about a person to begin sensing the resonance of their Persona or Shadow.
Thus, complete strangers will likely miss each other entirely, unless they are both tremendous talents; some sort of relationship, whether it's teacher to student, friend to friend, or even long-time enemy to enemy, will make this much easier. Even more esoteric relationships can sometimes have an effect; those whose Personas or Shadows are mythologically connected in some significant way (or in rare cases, are the very same figure) are much more likely to sense one another immediately, for good or ill.
Detecting resonance is consent-based, as is reacting to resonance. Not everyone has the talent, for one thing, and it is possible for another party to hide their resonance. Only detection-oriented support types, as detailed in Support Persona, can override 'hidden resonance' of this type, and even they are overriden in turn by those of the obfuscation-type of their talent.
Civilians may at times pick up on aspects of a character's resonance. This always translates as 'a feeling about that person' rather than the more colorful results Shadow-Possessed or Persona-users receive. While this can be beneficial in some cases--someone with a relaxing resonance may find people around her pick up on her 'constant sense of calm'--it can be detrimental. Someone with a fearsome warrior-like resonance will have a hard time being a salesman.
Hiding resonance is similarly easy. A character only has to focus on 'obscuring' themselves for a moment or two to rein in that aspect of their psyche. They simply fall off the radar completely for the vast majority of characters trying to seek them out. This, as mentioned, can be overcome by detection-oriented characters.
* As implied by this file, Shadow-Posssessed function with resonance exactly as do more conventional Persona-users.
* There is nothing about a particular character's resonance that labels them as specifically Persona-users or specifically Shadow-Possessed. Their status cannot be determined in this way.
* Evoker users may possess and detect resonance as usual, as however their respective players desire. Their use of a tool does not dampen or affect their ability to detect or project resonance in any way.
* Resonance is consent-based. Please be respectful of other people's wishes regarding resonance. Do not simply assume that you can sense that an individual is a Persona-user or a Shadow-Possessed; this is exceptionally rude, doubly so if one arbitrarily declares how the target's resonance feels without any discussion. The IC reason someone wouldn't be detected is up to the individuals at the scene, but resonance is not a sure thing, and so it's perfectly natural for someone not to notice another Persona-user or Shadow-Possessed without a compelling reason to do so.
* Only support-oriented characters may have additional resonance abilities outside potentially detecting other Shadow-Possessed or Persona-users, and hiding their own resonance. Please see Support Persona for what this entails for these characters and RP abilities through combat abilities what powers they may possess.