Villains are often the one character that get the short end of the stick when it comes to character development; however, in Monogatari's case, we finally get to see a brighter side to Kaiki Deishuu -- and it isn't just the clothes he decides to wear either. And switching from most of the focusing being on the many girl of the series, it came as a bit of surprise to see Kaiki's gloomy face show up.
With a character's main profession being deceiving people, and his motivation of maximizing profit while reducing losses, like cutthroat business man, what could possibly be there to like? Well the reasoning gets mixed in pretty well within the conversations between Senjougahara, Sengoku, and Hanekawa; whether you dislike what Kaiki did to Senjougahara, he still has this glimmer of good that justifies his action a little bit -- or Kaiki seem to justify it in his own head -- and this makes him a lot more human, and a better villain as a result.
Right from the start of Koimonogatari, Kaiki was presented as the person you need to be careful with -- in regards to his words. A bit later this factor turns into foreshadowing that will be missed if you did not heed his warning. And we are kicked into an almost sceptical look at a character that has already been introduced previously, but we only really know him for his past deeds. So we are stuck in a feedback loop of not to trust anything Kaiki says, and the impression that he is a bad guy.
So when the first call from Senjougahara happened, it served as a quick way to warm up the viewers to a character who we will be following in this arc. And it worked well for me because it was two characters that barely change their facial expressions, and demeanor, messing around with each other on the phone. It made for some great dry humor that continued throughout several of the conversations between Kaiki and Senjougahara.
And that back and forth between the characters displayed, quite clearly, how close they use to be before Kaiki severed all ties and ruined the Senjougahara household. But of course there was an explanation of why Kaiki did what he did, as I stated in the introduction paragraph; and this is where the gray area of a villain like Kaiki comes into play.
With all these factors of further establishing the relationship between Kaiki and Senjougahara -- addtionally getting to know Sengoku's secret hobby -- it was pretty clear that Koimonogatari was one of the better arcs to end on. It not only was enough to make a villain more likable, but took a different approach of interaction between characters. Rather than from many of the peers of Araragi, it was from the stand point of someone that hasn't been developed, who helped make the wrap up that much better.
And that leads us into the whole foreshadowing bit that was mentioned at the start of this arc.
To paraphrase, "...by the end you will be saying it serves him right", this was pretty much a lie on Kaiki's part and that was on purpose. If we are talking about the arc Koimonogatari, with the ending cliffhanger being him bleeding out in the snow, I have the opposite feeling right now. Though I wouldn't say he is dead for sure because we spent quite a lot of time developing his character and to kill him off so suddenly doesn't seem that logic.
Regardless, during this arc we pretty much come full circle; from the start, some might of downright hated Kaiki as a character, and rightfully so. However, by the end, we got to know him enough where we can, at a minimum, know where he's coming from. And that makes an ending like this both good -- because Sengoku is no longer a god set to kill two major characters -- and bad. And this is the power of developing a villain who has legitimate goals and isn't motivated by simple being someone who is bad.