First off if you have not watched the Kurokami anime there is really no reason you should watch Tora to Tsubasa. Kurokami: Tora to Tsubasa is a good fan add on to the final story. It takes two side characters who had a vague but important role in the main story and develops those characters into two somewhat enjoyable characters to watch. It was worth the watch after watching the whole season of Kurokami just to see how they interacted but if there was more episodes like this one i dont think i would continue to watch.