The reaper family occupies entries 77-79 in the Noise Report.
Noise #77 - Tenor Reaper
Noise #78 - Baritone Reaper
Noise #79 - Bass Reaper
Nearly all of the Reapers use a blast of energy that does minimal damage. They have a shadow in the other zone that can transition between the two zones freely. Keep in mind they take bonus damage from positive psyches. Regular reapers move away from Neku when he approaches them, so this can be used to your advantage to corner them.
Bat • Boomer • Carcin • Corehog • Drake • Fox • Frog • Grizzly • Jelly • Mink • Pig • Popguin • Raven • Rhino • Shark • Shrew • Sprog • Wolf • Wooly • Reaper