About the auction house arc and the mask
[Spoilers for volume 31!!!]
So according to Clara, rumour has it Kuromisa attended the auction looking for the six-eyed mask (aka the Natori family mask), which means that Matoba (more likely his entourage) was asking around for it.
There is always the chance that Matoba did not know about its connection to the Natori clan, but with how knowledgeable he is when it comes to yokai and exorcist politics, I don't find that very likely.
Matoba probably attended the auction for a plethora of different reasons (multitasking legend), but his interest towards the mask (and the story focus on it) is...intriguing.
Even if the mask was meant to be a convenient excuse for his Kuromine Misa cover, he could have picked literally any of the other items on display. Why pick an item with such an obvious link to Natori?
Option 1: Matoba is trying to get his hands on it to gain some kind of leverage over Natori because he still doesn't trust him. Not super likely now that they are on better terms, but who knows!!! This option would lowkey be kinda funny at this point in the story.
Option 2: The intel about the vase that Natori gave him meant a lot and he's trying to repay the favour somehow so as to not owe him anything. Information for information. Isn't he nice. (something something sharing burdens goes both ways).
Option 3: Matoba wants it specifically so no one else can use it against Natori because that's his territory thank you very much and he protects his assets ok. He's normal about it.
Option 4: Matoba wants the mask for himself to try and trick yokai into thinking he's a Natori (microdosing a wedding).
