This story is contained in one or two of the anthologies of Akutagawa's short stories. The easiest to get hold of might be Rashamon and Other Stories or Rashomon and Seventeen Other Stories.
I'm hovering on the brink of giving this particular short story 5 stars, just for the premise alone. ( Having more than one protagonist (or no specific protagonist at all) , and the differing viewpoints that these protagonsists have on the same set of events.)
The translation also came across as a lot more elegant than some of Akutagawa's other stories. I've heard that the film that was partly based on this story, Kurosawa's film "Rashomon", actually improves on the characterizations, and if so, I don't want to give the story top marks if it could conceivably have been even better.
I'll write a proper review once I've had a chance to view the film.
In the meantime, may I once more express my disgruntled irritation that GR doesn't allow for half-stars, in which case I could have slipped out of my predicament by giving this 4 and a half stars.