The internet is a magical place. I posed a question about the circumstances around the publication of Shinobu Kaze's Violence Becomes Tranquility in Heavy Metal in 1980, and within a few days the exact right person to answer that question came and filled us in!
Many thanks to Dan Steffan for this super interesting anecdote:
I worked in the art department at HM during Ted White's year as editor. Besides editing two sf mags, he is also the author of 17 books -- including "The Great Gold Steal" a 1966 novel about Captain America. He was also one of the first comic fans from the early 1950s, among many other things.
Anyway, as far as I remember, "Violence" was a blind submission to the magazine. It may have come into the mag before Ted got there, as there was a huge pile of material that had accumulated, but was never looked at by the previous editor. Ted pulled it out of the "slush pile," and put it into the magazine.
I'm not sure that many of us had seen much in the way of manga before this, except for perhaps Tezuka, but we all thought it was worth publishing anyway. But the thing that really cinched it was the fact that the strip very closely resembled -- in rendering, design, and coloring -- the work of the French cartoonist and fantacist, Philippe Druillet.
Druillet was one of the founding partners at Metal Hurlant and HM had published as much of his work as we could get our hands on. We all welcomed the opportunity to publish something else that seemed to be inspired by his work. "Violence" fit the bill.
The fact that the strip was from Japan was cool, but it wasn't really the main reason why it was published. I hope this helps fill in some holes for you. Thanks.