By now, the themes in Nisemonogatari are becoming increasing clear, especially considering the revelation at the end of Episode 10. In hindsight, so much of the story, even when it seemed there was none, was meant to convey who is a fake and who isn’t. But even more to the point, I think one thing this series has done just as well, though with a bit more subtlety, is who knows if they’re a fake and who doesn’t. One man who made it perfectly clear that he is a fake is Kaiki Deishu, as he readily admitted to the fact that he was a con man whenever confronted. That said, aside from his theme music, he isn’t anything we haven’t seen before in this series. But what makes him truly important, and thus an interesting study, is that his presence allows for the flaws of the main cast to become more apparent.
For further analysis, let’s go back to episode three when Koyomi meets Kaiki for the first time (see the caption). Koyomi almost immediately notes Kaiki’s aura is similar to his old “mentor”, Oshino. Since it’s pretty well understood that Oshino helped Koyomi in solving his problems back in Bakemonogatari (although in a fairly roundabout ways), only to disappear before this series, it would seem that we are supposed to infer that this is Kaiki’s purpose as well. Fortunately, this series only depicts far less themes than Bakemonogatari, which allows these themes to be overly apparent and identifiable (This in addition allows more time to be spent on witty banter and appealing imagery). As noted before, Kaiki is a very one-dimensional character, in that he is a con man and is very up front about it. This is completely in contrast to the much of the main cast who have all similarly convinced themselves that their lives have and will remain unchanged, and that there will be no consequences for their inaction.
This includes Kanbaru presumably waiting out her time at home until she is old enough to leave, Koyomi still believing that his vampire capabilities are as strong as they once were, or Tsukihi trying to fit in the Araragi household even though she is a Phoenix (as of this writing it isn’t clear of the exact circumstances behind the Phoenix and Tsukihi, but whatever the outcome, the analogy will still be applicable). However, the greatest perpetrator of convincing herself that her life will not change is Hitagi. She knows Tsubasa could very easily pull Koyomi away. From what we’ve seen, it has been implied that she has gone to extreme lengths to please Tsubasa to keep her from doing so. Hitagi even fast-tracked her relationship with Koyomi to seemingly solidify her position. However, with one of the instigators of her stress returning to town in episode 10, you have to wonder if everything Hitagi is doing won’t come back to bite her in the ass one day.