Well, from the very opening frames of this anime you know you're dealing with a card carrying member of the `magic warrior' genre. So if you can't deal with super-powered types fighting it out there's probably nothing here for you.
Incidentally there's an `anime inspired' fighting game out at the moment with the same name. Additionally it is planned that there will be a comic released (by dark horse) to go with the game. While both these titles share the same name, that of a mythological Japanese monster, there is no other connection between them.
The story begins with us following a young anime warrior. You can tell he's a warrior because he's got some weird armor and two swords on his back. And you can tell he's an anime warrior because he's got seriously exotic hair. He's pretty young, but seems pretty capable. And when the local villagers (this being a historical setting) are having problem taking on a wild boar he leaps into the fray. Strangely enough the visitors quickly turn on him, denying his help and insulting him. Indeed they call him monster and demon.
And when the boars awesomely huge parent arrives, and looks ready to tear the villagers into shreds, he exhibits super-human strength to save both them and, a little while later, a young village girl. In time it becomes clear that he's not entirely human, and the people in the area are very ready to blame every misfortune on him and let him know what they think of 'demons'. Only his grandfather, and the village girl, seem able to rise above this fear inspired tendency.
Things elevate to another level of power when an enemy group appears. They're a disparate band of warriors from the future, possessing great power, weapons and technology. They've also got some pretty complex personalities, and the group is not above a bit of internal squabbling and difference of opinion as to method. The one thing they do agree on is that modern humanity is facing extinction due to a cataclysmic drop in birthrate. And one solution to this is to go back in time and `prune' some of the less desirable branches on the genetic tree.
What they didn't expect to find is a warrior with the potential power to match their own. And, when our lead exhibits his full transformation into a huge armored monstrousity, he both foils their efforts and becomes the focus of their attention. While the villagers now consider him a confirmed enemy he gains some companions of his now revealed race, Oni (Japanese monster) to help him develop and survive. And, he retains the good will, and possibly affection, of the village female.
In other words all the pieces are in place for a long sequence of battles. The warriors from the future have great skills, weird powers and manufactured monsters as allies. They also have time-travel and teleportation so they're rather difficult to permanently defeat. Meanwhile the various oni have transforms into powerful monster forms which are fairly powerful, although our lead is generally the deciding force. In the middle is the sometimes hostile and often victimised mass of humanity.
It's certainly a fairly weird concept having the demonic monsters of the past fighting against the monstrous plans of the future humanity. Some generousity is required to accept this, and not pick holes in the plot, but it does add a degree of interest. Especially in the case of normal humanities role in the crisis. It's also interesting in that there is quite a lot of interaction. The Oni, in human form, are a loose-knit group of strong personalities. There's some quite entertaining dialog and character work, including a lively female oni. Meanwhile the villains are full characters in their own right. They differ over method, have personality aspects (such as the harsh honor of their warrior type, or the curiosity of their scientist) and backstories. They also feel their task is something that must be done, rather than as something intrinsically evil. It's sort of cool to see this more complex character environment than the typical `good' and `bad' guys.
Of course there are some downsides as well. The first is that story and character is limited by some pretty unsubtle character handling. Dialog and events are fairly simple and straightforward, with a fairly limited degree of complexity or subtlety. In a related limitation the characters are all safely super-powered rather than believable. The lead transforms into something that looks like a huge mecha, and the female oni trasnforms into a lithe (and bright pink, naturally) werewolf form and the future characters also have a very exotic appearance. It seperates them from the `human' background. But then again, the core of these series is super powered fights, so none of this comes as a suprise.
And the fights themselves are limited by the animation. It's not overly impressive and is clearly budget limited. There's some strange elements in design, and the general appearance is a bit cluttered and muddy. Motion is not too smooth, and is often agressively simplified when the complex `creatures' are fighting. This is aggravated by there being long, and overblown, transform sequences for the leads prior to a combat. Something that quickly tires. While it is quite watchable these shows often rely on impressive moves and powers during combat to make it more flashy and exciting. Something it seems this show is not too capable of. The voices were reasonable, partly because the simple dialog doesn't allow too much of the actors. The music was basic and minimal.
None of my regular sources have a review of this title. What's more, with the title being a very generic word (At least within anime fandom) I couldn't find a review anywhere on the net.