Ninja: Golpes Fulminantes

It starts with a European ninja in a black togs shooting magic out of his fingertips to kill two guys in the woods.

Then we cut to the main plot of villagers being terrorized by a local mob. Most of the plot involves this subject matter.

The ninjas come back about 30 minutes later with a European "student ninja" in a white outfit fighting his master (the bad ninja introduced at the beginning).

Then it cuts back to the populace being bothered by bad guys again.

The ninjas are only indirect aspects of this movie. Like spliced in footage from a different movie entirely. They never encounter the main characters and are unreferenced by the main characters. They are just very short filler bits (under 5 minutes each for the 4 scenes) to allow better VHS box art.

The alternate title I just updated lists this movie as "THUNDER SCORE" (no previous listings at IMDb). Thunder Score https://www.youtube.com/watch?v=iIsGjYYfn2c