When the sheriff is talking to old Quentin Tarantino's character the sheriff talks about Akira (his son) and Tarantino replies "every time I hear that name it touches my heart, what can I say, I've always been an anime otaku", (Japanese slang for a person that is a fan of anime, manga, and Japanese video games and culture) this is a reference to the classic anime film "Akira".
The introduction to the tale given by Quentin Tarantino's character is taken almost verbatim from the opening passage of the Tale of Heike: "The sound of the Gion Shouja bells echoes the impermanence of all things; the color of the saala flowers reveals the truth that the prosperous must decline. The proud do not endure, they are like a dream on a spring night; the mighty fall at last, they are as dust before the wind." (Helen Craig McCullough's translation)
Quentin Tarantino's character's name, Piringo, is probably an amalgamation of famous Pinkerton Detective Charlie Siringo, and famous outlaw John Peters "Johnny" Ringo. It may also be a reference to the "Ringo" films starring Giuliano Gemma.
The trivia item below may give away important plot points.
The machine gun found in the coffin is a clear reference to the 1966 film "Django" in which Django himself carries a coffin for the majority of the film only to reveal he too was hauling a machine gun.