Old Karate Movie

[abyss mind]

I am looking for the name of this old Samurai / Ninja movie.

This movie is I think during the 1970's - It is about this white dude who is being taught the ways of the Samurai and he likes some chick in the movie, but anyways in the end the clan of Samurai have to go into this giant building/complex of ninjas and defeat them all and even though the white dude ain't that good of a fighter he ends up being the last guy left and kills/chops the last ninjas head off! What is the name of this movie??

Also I think that it is in black and white?