This is an excellent ova, its bad they didn't continue doing it, i heard a lot of people saying i thought it has something related to ninja scroll, please don't think just because the font is like each other its gonna be related, first you have to investigate a little about what you are going to watch. I like very much this ovas, because in the bottom this is a real story they just took it and add some gore and mystical ninjas, this is one of japan real stories of feudalism, so i insist first investigate instead of saying its bad, cause its very goodanimation.

If want to know more from this just search for the movies, Ninja Resurrection there are a lot of them with people, actually there is one with sonny chiba as yagyu jubei. So just watch all of the history behind anime and you'll understand the thing better