I think it might've come out in the 70s or 80s, although I'm not sure. It was about a Japanese (i think) warrior that was sent to europe to negotiate a deal to obtain firearms (like muskets or something) for his country. At least that is what I thought was going on. I seem to recall he had to safeguard the payment which was like a big chest of gold or something. Somewhere along the line though he got screwed over by somebody, and the film ended where he killed the antagonist, wearing a shiny suit of plate armour, by the seaside.
The scene that I remember best was where this one pompous noble/knight character, who I believe was the film's antagonist, was showing off the sharpness of his sword. He stuck it in a fountain, and then threw some rose petals in the water. After a while the rose petals drifted towards the blade and were cut in two. The protagonist then stuck his katana (i think) in the fountain and after saying some prayers, or simply meditating, the water around the blade started to boil. He then took his blade and cut a nearby suit of plate armour in half, to the astonishment of a crowd.

Lol, yeah, I also instantly thought of this one. I was thrown off by the "70s or 80s" thing, though. When I saw it on German TV it was simply titled "Shogun", though. Also I wasn't aware that Christopher Lee was in it, dang.

Just remembered: This movie made me a man. I couldn't stand the sight of blood in films *at all* until a certain age, this was the first film with a certain amount of blood that I actually sat through without any trouble. Don't know why this particular one.

I actually remember an episode of Magnum PI that had a similar plot to this movie. I wonder if that was intentional.

That's it thank you very much!! I think I might even still have a recording of the film on VHS at my parent's home