Usually, I'd be nice and give this a 5/5 stars, but I think this has some actual potential. So I will give you advice on how what I think will make the series better. But first, complaints:
First off: what bothered me the most was the inconsistent character models. They were good, yes, but they were inconsistent. One looked like he had much more detail than the other while one looked like he just had eyes and a fake beard on. I would like it if you either somehow give them all the same "base". If one has black lines to show where the nose is, everyone else should have one or he shouldn't have one. If everyone has the same eye style, this guy shouldn't look like he was torn straight from another anime. I think you get my point, if not, here's an easier example: If you're making a Dragon Ball Z Movie with Attack On Titan Characters tacked on, it would look very weird to see two different art styles meshed together.
Next off: The Animation. I know, this isn't a large studio, but please try to make them a little more "life like" when they move.
Then there's this: The characters and plot. Frankly, I have no idea who anyone is and where they come from. I don't know why they're fighting or what time period this is. I don't even know half the characters. Speaking of characters, they're very forgettable and not relatable. Sure, the "Lord" or Shogun or whatever he is, is a badass. Frankly, that's all I got from him.
There's also this: Pacing. Too fast. Too soon. I have no idea what's going on. Things happened way too fast without any real back story to it. I don't think just one scene explaining that this Lord has to be assassinated will tie everything together.
Finally, the fight scene. Awesome, yes. Style? Inconsistent. At times, you show them fighting slowly where later they start moving at fast speeds. The spinning was also a little bit weird. Typically, one would just step back or in fighting game mechanics: Dash back, while this guy...he spins. How does he not get dizzy? The fight scenes lacked any real effects. I mean, you got the camera shaking right, but I'll get to that later. There would usually be a small spark or bright light when swords strike each other. That really bothered me when I didn't see anything like that. Also, there is how slow the character models moved. I'll be honest here. If I was fighting someone who moved that slow, I would have probably killed them in the first two seconds.
How you can improve:
Character Models: You could try editing the models. Then again, not my expertise. While I don't have anything against the models, the fine details really bothered me.
Animation: You could try watching yourself in a mirror, watch every detail on how you walk or move, then try to mimic that as precisely as you can. You can also take some time to add in those little details instead of skipping over them.
Characters and Plot: Nothing I can really do here. I have no idea what's going on. It's like watching an entirely new series while starting on the 2nd or 3rd season. Best if you link me a prequel if you have one.
Pacing: Take time to explain the story more, show motives, character reactions, etc. Heck, what I do is try to write the character's reactions and what they would do to prepare for it. Then time skip to the actual fight. Basically: DON'T RUSH IT.
Fight Scenes: Ah ha, this is what I'm going to focus on the most. Fight scenes are typically better when they're fast and move realistically. You can have the craziest fight scene on Earth and as long as the characters move like how a normal human would move with those abilities and in that scenario, it's a good fight scene. If you make the fights about 2x as fast, that would have been a pretty sick action scene. People don't need to see how the characters move in fine detail, they just need the gist of it. Sure, you can add detail as long as it's fast and keeps the pace fast. We also have sound effects, visual effects and camera. Sound effects are fine as they are, maybe add a little bit of wind and kicking noises for when she tried to kick him. For visual effects, try motion blurring and sparks. Motion blurring for when the ninja girl moves at fast speeds to emphasis on the speed and sparks for when the swords clash. As for Camera, if it's shaking every time the swords clash (as in a very sharp shake), it would make the fight seem much more intense than it really is.
Note: I can't explain everything in words. It would be great of me if I could just...show you. But that would be too difficult for me and I don't have the resources (well the software anyways) to do so.