Karen interrupts her brother’s studying to show him a new look, wearing Tsukihi’s clothes. She knows he knows Kanbaru, but Araragi won’t introduce her to her unless she wins a “game” involing him brushing her teeth. It goes a bit far, and Tsukihi walks in on them and isn’t pleased. When she storms off, they continue the game.
Nisemonogatari reaches new heights of creepy sibling interactions, specifically Koyomi enjoying brushing Karen’s teeth – and Karen enjoying him brush her teeth – a bit too much. We can expect Koyomi to act like this: he’s been interacting like this with girls – particularly younger ones – all season. And he’s part vampire, making him literally not entirely human. But what, we wonder, is Karen’s issue? On second thought, eh, perhaps it would be best if we just not wonder and simply move on, shall we? Tsukihi comes in and breaks it up, only for them to get right back to it when she leaves.
Clearly Akiyuki Shinbo does not have any particular qualms about dealing with these kinds of issues. If there is a taboo to be exploited, he’ll put it right up in our face, as close and intimate as possible, not skimping on a single facial expression or sound of enjoyment, while staying right on the edge. Indeed, this was perhaps the weirdest -and wrongest – tooth-brushing session we’ve ever witnessed. Tsukihi seemed to concur.