I personally don't know about Kyou, but I theorize that
iamandragon herself IS a tsundere. Of course, so far all we've seen is the tsun-tsun side of her, but maybe there's a dere-dere side to her that we haven't seen yet.
(J/K)
Joking aside, it's almost the same case with Kyou. Maybe what we see is the tsun side of her, maybe it's not, but we still can't say whether she is a tsundere for certain until when (of if) she shows a more obvious dere-dere side of her.