You either like the style used in this series, or you don't.
If you want to know wether you should watch this or not, I'd say "NO, there is probably something better to fill your time with". If you want to kill 10-15 minutes with something "light" and short, feel free to give this try. If you still want to watch the series after watching the first episode, go ahead. If you don't, then you shouldn't expect the series to "improve" in any way over the next 25 episodes, since the "quality" will stay constant.
Now, for a more detailed review:
The plot itself is quickly summarised, somewhere in a different world, there are crazy/powerful people running around who possses something called "Ninja souls".The series literally begins with our protagonist dying after a certain ninja obliterated the whole block in order to kill some other ninjas. Sadly, all that happens off-screen and before the series begins. During the offscreen-destruction, the protagonist's wife and child were killed (they only appear in the intro and 3-4 short flashbacks) and that's why our hero gets "possessed" by another Ninja-soul who only wants to kill other ninjas. All so he can go out and get revenge for his family (The family never gets fleshed out. All we get to learn about them are their names, and that they're dead). This is about crazy people/ninjas killing each other with absurd techniques/skills.
Now that we have our explanation why the hero becomes a ninja and goes around fighting against other ninjas. Other than that, there is very little plot. Sometimes, there are side-characters who cross the path of our Ninja-Slayer, and sometimes they get their own story arcs which stretch over 2-3 episodes, but the core of the series is about Ninja Slayer slaying ninjas. The rest is just a short change of pace.
Which brings us to the next point, the animation... 80% of the scenes happen in a 2d perspective with (static) cut-outs of the characters being moving around. From time to time the scene switches over to "normal" animations, but in general you can expect to see a the 2d-perspective. It's not that bad, the mix between 2d and 3d kinda works and the scene flow into each other... what really bothered were the repetitions:If it was only once or twice, it wouldn't be that bad, but sometimes the exact same animation is repeated 4-5 times, and the only reason for that appears to be the need to fill the remaining minutes of the episode. It happened often enough that I had to fight the urge to fastforward everything...
The sound is okay, and unless you have problems with many characters shouting "YEAARTT" or other repetitive sentences there aren't any issues. Characters are "okay", and their development is minimal. After all, this is about Ninja Slayer being on a quest for revenge...
Summary:If I had anything else to watch, I wouldn't have stuck with this series for 26 episodes. It serves as an excellent time killer, but compared with everything else that was running... there are better series. As I mentioned in my first line, some people will like the series, and some won't.I think the series rated a "Meh...", and I wouldn't watch it again. I do not really know who produced this series, but I often had the impression that this was something a student or intern made as a private project to get some experience on how to animate a series. A one-person-project if you want... why this was aired, I will probably never understand. It kinda feels like something that belongs more on a website for flash-animations than television.
