This Omake consists of several small acts:
Act 1
Kunikida and Takeuchi beheading Momiji. Kunikida triumphantly declares, "I did it!" and then is nonplussed when Momiji sprouts spider legs (like an Aragami) and skitters away...
Act 2
Momiji and Kusanagi under a cherry tree; it seems that Momiji is trying to tell him that she likes him, but all that seems to be coming out is the name of famous Sumo wrestlers... go figure...
Act 3
Kusanagi in a desperate battle with an Aragami. He lunges, stretching his arm out to strike at the feroucious monster, when, lo and behold he misses and his arm doesn't retract. How embarrassing!
Act 4:
Kunikida's lethal joke. He lets Momiji read it. She dies laughing. He wants to test it on a guinea pig: enter Kusanagi. He dies reading it, and then you find out, it wasn't really necessary to test it, since all the Aragami were put to sleep when Momiji died reading his joke in the first place... Oh, the irony.