Reiji in the anime was flat out insane and volatile. All those dreams about stabbing people and whatnot are completely out of character. He's not the healthiest person in the world in the manga, don't get me wrong, it's just that he's quite differently problematic there. He seemed in character in the OVAs but the way they handled him in the anime was so that they'd have some form of conclusion with the story in a place where the manga seemed to not end for quite a few years. (and it indeed has not)
I'm not sure how much you've read btw but he has gotten quite better lately.
I'm not sure how much you've read btw but he has gotten quite better lately.