Aye I'm all for the theory that Yukari = Maribel to. Gives a nice achillis heel to the Great Border youkai.
She's a special friend to me as well.
Special thanks to all you readers~I'm an advocate of the Yukarin=Merry theory, so that ended up entering into the story as well.
Wonder what the future holds for the Secret Sealing Club after dropping a bomb like Sumireko-chan, huh...?