I played through the Oni PC demo and I thought the same thing some of you ahve mentioned. I hope the PS2 version looks/performs better! For example, when you kill people in the PC demo they will fall down and lay through a wall. And as the camera follows the player (in 3rd person) sometimes it lets you see through walls (other similar games will zoom closer to the character to avoid this problem). These things really detract from ones immersion into the game. But this is only a DEMO
Otherwise, I kinda liked the game. I have to agree with JackZ that it is a lot like Messiah, but it has more fighting game thrown into the mix. The main character really has some cool fighting moves and combos. I thought the enemy AI was pretty good too.
The game has a strong Anime flavor which was also cool.