It's robots vs. ninja, basically. However because we're back in medieval Japanese history, these robots are "puppets". They're made of wood and they have strings.
The story's short and simple. Ninja attack a castle, discover something terrible and get shredded. (We'll learn the details later and they're disgusting.) That doesn't take long. The story's main characters are: (a) the last surviving ninja, Manajiri, and (b) a princess called Rangiku. They're up against the local feudal lord, Lord Karimata, who some time earlier sent his army to attack Rangiku's father's castle, steal his puppet warriors and massacre everyone.
There's strong emotional content, with a fantastically gross secret behind the puppets even if it doesn't make much sense. It's certainly enough to motivate Rangiku, though. We also have bad guys who are happy to beat a child with sticks because it was walking slowly and then to beat its mother for trying to protect her child. They're scum. You want them dead.
However it's also an action anime. Puppets vs. ninja! This is cool, but don't think about it too hard. These puppets aren't dangling underneath their puppet master (instead often being above them!) and so there's no tension in their puppet strings. It shouldn't work. The physics is nonsense, although this barely counts as a criticism in anime. Anyway, these impossible puppets can run through trees and even climb them. They're also superhuman fighters and might win a battle against proper SF robots, despite the fact that this is the 16th century.
Nonetheless the OVA gets away with it. Firstly, the puppets also have wooden clockwork parts and gears. Secondly, we're seeing the drawbacks of this technology. The puppet-master needs defending and you'll be screwed if your opponent attacks your puppet strings.
The important thing for an audience is that all this looks cool and it's being done with vim. The art style is rough-edged and sometimes kind of ugly, but it's blood-splattered and great at action. My favourite thing about the animation was the movement of the bad guy's puppets, in a flopping, zombie way like Olympic sprinting rag dolls.
However at the same time, the characters are fun. There's Slayers-like comedy, which I liked a lot. Even when it's not funny (e.g. Rangiku always mispronouncing Manajiri's name), it's giving the OVA character business to play with, instead of being the one-dimensionally grim and bloody affair it would otherwise have been. Besides, it did make me laugh. Rangaku's ridiculous backpack is funny, as are the moments with the money and the flower. The only bit I disliked was the lengthy scene where we're supposed to see amusement in Manajiri turning into a sexual predator and attempted rapist, which also has extensive Rangiku nudity (with nipples). Ho ho, piss off.
There's even a historical reference in Kato Danzo, a famous 16th century ninja said to be capable of sorcerous feats like flight. There's a story that he swallowed a bull in front of over twenty people and the opinion has been aired that he was either an illusionist or knew a kind of group hypnosis. That explains the "dissolving into smoke" scenes, which seemed weird even once I'd accepted the killer wooden robots. However even if you hadn't heard of Danzo, you'd guess that he was someone significant from the way he's name-dropped.
Bang Zoom! Entertainment's English dub acting is regarded as horrible even by people who like English dubs, but obviously I ran a mile away from that.
Overall, it manages to be memorable and tell a complete, satisfying story in 42 minutes with character development for both leads. Manajiri transforms himself from "scum" to "stalwart", while Rangiku is a highly sympathetic protagonist. There's a chunk of objectionable material in the middle, but at least in the end that's resolved harmlessly. It has striking art and it's unexpectedly well animated. It's good.