Okay, here's what I currently think is going on.
In the
first video in the series, Miku (the red-haired one) states that the Spider family was abducted by the Fox family and is being tortured by them, then starts like she's one of the Spider and curses the Fox to be cannibals while Gumi (green hair) is getting all aroused by disemboweling Miku and towards the end of that video starts commenting on the taste too.
In
Will-o-the-wisp Gumi is blaming someone for defiling her and telling them to die soon, and once that she wants to eat them. While Miku appears as a contorted outline on a black background asking "Do you know my suffering, do you know my sorrow?" and listing various disfiguring tortures.
In "Beheading Dance" someone gets decapitated, I cannot for the life of me figure out who.
So I'm thinking in "The Fox's Wedding" Miku is a ghost or something wearing a fox mask to mock her killers and making Gumi fall in love with her and marry her, while Gumi wants to eat Miku's corpse and Miku is pointing her towards it so that when she eats it they can become one.