Keigo eyes Tonbokiri's tube of probably mercury.

"Remember I said it was like magic chemistry?" Keigo picks up a glass apparatus. "You could put some chemicals in here - but don't open that one you're holding! - and maybe heat them up and wait for them to react and then see what comes out."

So maybe they've found a sort of alchemy lab in the woods, but there's still one big problem.

"The quest said find the Philosopher's Stone! It didn't say make one!"