The last of the 3 original Wataru Series. It would be best if you've seen the original, but you should be fine if you want to start here. It doesn't really matter if you've seen 2 or either of the OVA sets, since this pretends they don't exist. Just like the prior series, this has a monster-of-the-week format, and around every 5-10 episodes they clear a particular setting and head to a new one. The final 10 or so episodes are dedicated to wrapping up the main conflict. This one's a real heart breaker. From what I can tell, Chou is considered a fan-favorite (at least, ifthe JP Blu-ray prices are anything to go by), and there are some good reasons for that. The first two-thirds really just work. But the last third really, really drags the whole experience down.

One of the good things is that the main trio is at their best here. Himiko was dramatically improved by using her a bit less overall and a lot more deliberately. Shibaraku is in peak condition. Instead of being a buffoon, he's generally competent. The wider recurring cast means he has more interesting banter overall. Wataru "loses his heart" at the start as part of a scheme by the main antagonist, so he acts less generically heroic (for the start, anyways). This gives him a little edge that makes for some fun moments and it gives Shibaraku more chances to act as a proper mentor.

Another plus is that the baseline episodic plots are at the best we've seen until now. If you pick a random episode, it'll probably be better on average than a random one from either prior series. The ideas are solid and whimsical, and there are a number of memorable moments and gags that land well throughout.

Another small plus is that the mech powerups were interesting for once. The original series and 2 both just had halfway powerups, but this one gives Wataru a new mech transformation at the end of every layer. The total amount of time spent on transformation sequences is about the same as the prior series, but there's more variety in that they have several different sets of reusable transformations sequences (with unique music each to boot) instead of just one or two. And it makes the actual fights more varied, since each transformation has different signature moves. Of course, every fight begins with the summon and ends with the final slash, as it always has.

Visually, it's a big improvement in most ways. Jumping from 2 to Chou, the picture quality is obviously better. The characters are much less flat and their style is a lot cleaner. And we see more expressive characters overall. But they are off model. A LOT. I didn't notice that much at all in the prior series, but some episodes here are just off constantly.

The new cast members are a mixed bag. Suzume is the better of the two. She's supposed to be a sometimes-ally-sometimes-foe mercenary sort of character, but she loses the mercenary edge before too long and with it, most of the fun. Her personal plotline is uninteresting and feels tacked on. It would've just been better to never give her a detailed backstory and have her become a real party member only at the very end.
Seijyu is a puppet without a heart, which I suppose is intended to parallel Wataru's situation. His issue is that he has no chemistry with the main party and rarely does anything. He talks a lot about learning what a heart is, and he even gets one at the end, but there wasn't much of a journey between. And his bizarre romance plotline with one of the antagonists would be great if it was compelling or endearing or something. It was very paint-by-numbers for an already flat character. Frankly, the show would be better if he was just cut entirely.

The new recurring antagonists are actually good for once. The Wataru franchise really likes having a trio of siblings play as long-term recurring antagonists, and this is the one time they're good. They have distinct personalities and have complicated relationships with each other. For most of the run, they're great at their role. During the last portion, their plotlines need actual resolving and oh boy do they make all of them boring and predictable. More importantly, they're LONG and boring and predictable.

Toraou once again makes an appearance, continuing his curse of only showing up in the second half of the show. It's a swing and a miss. He's lost his memory and is working with the bad guys. Which means roughly 100% of the dialogue between Wataru and him is "But we're FRIENDS," and Toraou being confused and dismissive. They also do a dumb brainwashing sequence. Which just results in the same energy but replaced with "I can't fight my FRIEND!" Aside from the incredible writing there, it really just feels like a rehash of the same idea from the original series or the betrayal in 2, both of which did it way better.

The core issue is that the show is bad at resolving with plotlines that last more than an episode. The first two-thirds or so of the show works well because it's resting mostly on once-and-done stories. The moment it tries to switch gears, it hits a wall and inches forwards against it for the rest of the run. They did a good job at teasing the deeper plots of some of the characters, but once they got to revealing the details, it just killed any interest. Genuinely, the show would've been better if they didn't try to resolve all of the plot threads in detail and just had a typical "we beat the bad guy and everything is fixed now!"

It's a good show overall, but the ending and the leadup to it leaves a bad taste behind.