The plot of Alien Vs. Ninja is...oh come one, it's in the damn title. A group of ninjas, led by a talented but angry young ninja played by Masanori Mimoto, are stalked by a group of aliens in the woods. They fight in sped-up action scenes that are only entertaining when those scenes revolve around make-up effects, like the scene where one of the ninjas has his legs melted down to just his bones by some kind of alien acid. Tis a silly film.
Admittedly, I don't think anyone watching something called Alien Vs. Ninja expects high production values or a story or alien costumes that don't look like someone took Barney and transformed his costume into something Lizardpunk, the latest in Nounpunk fads (Note: there is no such thing as Lizardpunk. I think.) fans might go for. If you can see it with a festival audience and are curious, that's pretty much the way to go. If not, well, um, there are things in this film you might like and there are a lot you won't. The fight scene that starts with an alien going for a boob grab is kinda funny. There are some other scenes, too. No, I can't think of them but I'm sure they exist.