Don't worry. It picks up soon.
And Hajime can be a little confusing sometimes.

Good. Kai deserves to be hated.
Climax is Den-O's final form, Liner is used when Ryotaro can't be possessed anymore (Also, if Sword is Momo's, Rod is Ura's, then treat Liner as Ryotaro's form).

So... will they be able to posses him later?

:lol for once we're on the same page when it come to toku characters we hate.

I'm answering yes. It's a minor spoiler, but it's about the "How", not the "If."

And Kai is a terrible, terrible villain. I've yet to find a villain in a series that was worse...

Ok, good.

Decade obviously...wait technically he's only a villian in some of the movies. He did cut GACKT's arm off though...

Kai is an uninspired villain but not necessarily a bad one. Shittiest villain I've seen in a while? Reiji from Kaubto. And yes Climax (or rather Super Climax in my opinion) is Den-O's final form. Liner is on par with it but it only came about because Ryutaro couldn't be possessed at the time.

Continuing with Blade. This really is picking up. I find it hilarious that every time Kenzaki tries to approach Tachibana, he either gets shot or lazily thrown to the side. The guy becomes a piece of jelly the minute he gets in proximity of Garren. And is it just me or does Kotaro's sister use every possible conjugation of the verb hajimaru when Amane is around?
This girl's obsession with Hajime is a lot more realistic than Gon and Daisuke, though.

Decade is just a horrible character.

I dunno. While it could be argued that he was alluded to early on, he seems pointlessly tacked on for the sole purpose of having a big boss villain for a climactic battle.

Glad you're enjoying it ^^

Oh yeah. This show is handling multiple riders really well, between Garren's drug abuse problems, Hajime's humanity, the Peacock dude's ultimate rider project, and Kenzaki tying it all together.
Well damn, there goes my favorite character. That would have been a lot more moving if Tachibana's actor bothered to, you know, act in that scene.

Yeah, but Super Climax is a movie exclusive form. I really wish it wasn't a Tamashii Web Exclusive, I guess I'll be fine with the normal Climax Figuart.

He just wants to take pictures of everything.

I do agree with the point that Kai feel tacked on, I think if they showed him in the beginning it would've been better.

It's okay, you're going to get a few episodes with Mika Hijii soon. Mika Hijii makes everything better. Always.