The story you are thinking of is not, in fact, named "Rashōmon". Its real name is "In A Grove", and it is one of two Ryūnosuke Akutagawa stories (the other one being "Rashōmon") that Akira Kurosawa fused into a single tale and adapted into his groundbreaking 1950 film. Comic artist Victor Santos has done much the same thing here, taking not only "In A Grove" and "Rashōmon", but also the tale of of the 47 rōnin, and using them as raw material for a mystery/thriller mini-saga. "Edo noir", I guess you could call it—two stories driven by a need to know the truth, no matter how convoluted, subjective, or disillusioning.
That incident in the forest...
The fulcrum for all of Santos's reinvented material is a character of his own invention, an Edo-era investigator named Heigo Kobayashi. Noir tradition demands certain things of its detective characters, and Kobayashi embodies them all: he's world-weary, both deeply conscious of and cynical of the evil that men do, but holds out what hope he can that things can be improved, and he has a code and sticks to it.
The first mystery he's confronted with would baffle better men. A nobleman has been found in a forest grove, dead of a single stab wound to the heart. The evidence is inconclusive; no murder weapon was found. But there are witnesses. There is Tajōmaru, the bandit who claims he happened across the man and his lovely wife, raped the woman and was egged on by her to murder the nobleman. There is the wife herself, who claims she killed her husband to spare him the memory of her violation. And then there's the dead man himself, summoned by way of a spirit medium, who claims he killed himself out of shame.
Akutagawa's original story, one of the finest in any language, leaves the matter more or less open-ended. Kurosawa's movie uses a wraparound device to present us with something like closure: a woodcutter who discovered the bodies, and as it turned out witnessed the whole event. Here, Santos also uses a piece of the original "Rashōmon" as a bookend, but the true conclusion is something he supplies himself. It is Kobayashi's realization that the woman has taken advantage of the situation for her own ends, and that everyone from the thief to her dead husband was all too willing to let her do it. It wouldn't be noir without a femme fatale, would it?
... and then that assassination business
By the end of the story, the woman is safely out of reach, set to be married to a man of power and influence who has taken pity on her. The second story, "Seppuku", Santos's reworking of "47 Rōnin," continues some time afterwards, and places her left-of-center (though still near enough to the center to matter) of a scandal involving her new husband. He's now her late husband, as he was the victim of a revenge plot orchestrated by former vassals whose lord he put to death. The question is not so much "who?" as "why?"—or, as Kobayashi interrogates those who knew the assailants and those who were spared by them, "what does it all mean?" And again, his search leads him back to that woman, who sits at the center of it all in ways Kobayashi is not prepared to appreciate.
"Rashōmon" and "In A Grove" were set in an era centuries before the events of "47 Rōnin", but Santos has not committed undue violence to any of them by setting all the events in the period of the latter story. The most topical detail I can think of that goes missing because of this is how Akutagawa used the setting of "Rashōmon" to evoke the decay and decadence of the era (the late Heian period, a time of unrest and disorder). There are also times when Santos has some fun with the trappings of the setting, as when it turns out Kobayashi is old buddies with the ninja Hattori Hanzo. But such changes don't make the flavor of the whole work inconsistent; it's ultimately all of a piece.
I wasn't familiar with Santos's work before this project (originally published in Spain), and so I regret not being able to compare Rashōmon to his prior works like Polar: Came From The Cold. I can say, readily, that Santos's style is an excellent complement to the story. It's not manga-esque; it's more in the vein of Frank Miller or Mike Mignola, with great swaths of solid color (and black, and white), heavy lines, silhouettes, and deep shadows. The cover gives you a fairly good idea of what's inside, right down to how one of the predominant colors used is red. It's not hard to imagine why.