The time travel...was OK?! It didn't even relate to the theme of vampires and iconic horror characters! Unless of course, you call Back To The Future! and other time travelling movies horror movies. Two episodes were wasted for the time traveling arc and the arc basically RESOLVED nothing. Neither did it explain anything beside Nago's button fetish. Which nobody really cares(right?).
Wataru may be an orphan, but that doesn't mean that he and Taiga can't havea duel to the death and then they both cry about it having to end this way. Like just how Shadowmoon and Kotaro went down that path. The way the Arms monsters talked about the "agreement" to Otoya, it was as if they went through an oath or something, but then it just ended up being an old cool "promise me, you'll take care of my son." They could had handled it way better than that. As for the ending be okay as well? Seriously, UFOs may be an iconic horror character too but, the way they mixed time traveled, neo-vampire-fangires, and Otaya coming back as Wataru's son and making an annoying entrance? Just no.
Kiva had a lot of potential, but like Decade, it's all wasted. The first vampire based Kamen Rider. Meh.