"Should we try opening it?"

"Yes."

All right. Here goes.

Sayuri breaks the seal, and opens the door... To reveal a stone room with a large box like a coffin in the middle. It's closed. 

Not ominous at all...

"That looks big enough for a person," she murmurs.

"Not a good sign..."

"I'm guessing there wasn't anything like that in the catalog."

"No. Though I doubt something like this would have been for general sale."

"Not for sale at all, probably."

"It could have been a commission, but... This was most likely a project meant solely for the village. Perhaps a guardian..."

"What are we waiting for? Let's look inside."

Then Tsubaki will move the lid aside.

It's... Empty, though there's a very suspiciously person-shaped depression in a bed of wood lightly padded with cloth. 

"That's not good."

"Nope."

"Only question now is if they escaped or were let out..."

"The door seal had been repaired. I doubt this thing would have stopped to fix that."

"It's possible if they knew enough about seals - which isn't too hard to pick up when you're stuck in one - and were cautious enough to try to hide their escape."

And then, somewhat sharply: "Youkai are people. We aren't mindless."

"...Sorry."

Sigh. "Just - try to keep that in mind. We're either dealing with a person, or a tool being wielded by one. This isn't some shōnen manga where you run around guiltlessly punching monsters." 

"I just meant- most youkai that I've seen that had been locked away don't really want to touch that kind of seal again."

"Embodied youkai tend to be sneakier and more patient - given the example of the cats, I suspect the potters would have made something that developed its own soul, rather than trapping an existing spirit. Those are inclined to hide themselves, and they're more aware of humans and human activities."

"But... The White Mist potters don't create weak seals. It would have been difficult to escape this without help - at least, in the time that's likely passed."

"How long do you think that is?"

"Somewhere around fifty years, though could be as long as a century."

"That'd be my guess, too."

"Would it be possible to look at the seal on the door and estimate when that was broken?"