It's hard to rate films like this, because do you rate it on production or just fun?
I saw this film back in about 1988/89 or so when I was a boy and I'm sorry to say it started a life long fascination with ninjas. The plot is fairly dire and the acting is of course terrible, but there is a certain mystique surrounding the ninjas in this film which makes for quite a good atmosphere. What is important are the fight scenes, while a 'little' sparce, are really good.
I must say it was better when I was a boy, only now can I see the glaring points of unbelievable nonsense in the film, but as a "sit back with a few beers" martial arts film I can't fault it, it delivers and is much better than the mountains of "American Ninja" Style rubbish that was churned out in the 80's with hundreds of guys in black suits but really not very good fight scenes.
In an interesting note, Dusty Nelson, the writer and director of Sakura Killers did another ninja film under the Bonaire movie flag called "White Phantom" I have no idea if this was meant to be a sequel to Sakura Killers" but the Sakura clan is once again a main feature, including the same logo and similar story only this time including a White Ninja. This too, while being mostly dire, had a small sense of atmosphere but the fight scenes are even more sparce and to be frank, are pretty awful.
So, if you are a martial arts fan then give it a blast to kill a few hours!