So Kanonno has this thing. Where she sense/smell magic. Specifically mana, but let's go with magic in general for the sense of potential plotting.
It's a very passive ability, where she may or may not notice. Usually, she needs a reason for her to be wondering about it before she can notice. For example, when she accepts that the Terresian Descender is not human, she realizes he smells just like the mana that created him. In most cases though, scents are used as a way to point out the differences between the mana of different worlds.
HOWEVER. Upon entering Saeng Seong, she can't tell the difference between the mana of different worlds. My unofficial stance on this is that she can only smell the scent of mana (if any) permeating the area or very concentrated instances of mana (such as a world tree seed or in some cases, a Descender), not the individual manas of people walking around.
Despite this she should still be able to sense different characters to the magic of different people or spells e.g. things she has noticed in canon are if mana is hard, soft, rigid, malleable, if it has a flow or direction to it, if it's connected to something else, or if it's being blocked off by something.
So if there's anything you want her to notice for plotting purposes, drop it here.