Karada Sagashi

A cryptic request received out of the blue: "Hey, Asuka... search for my body". This is the start of how Asuka and her friends end up searching for scattered body parts in the middle of the night. If they don't find the entire body, 9th November is repeated and the red person will continue to kill them. Who is the red person? Why is Haruka asking the 6 of them to search for the body parts?