Slicer Brothers

A pair of serial killers who had their souls sealed into a single suit of armor (one sealed in the head and one sealed in the suit) and became one of the guardians of the 5th laboratory under the joint alias of "Number 48," assigned to kill any intruders.

In an omake (a short bonus comic), the older brother is a cat lover while the younger is a dog lover, which leads them to bicker at times. However, the younger brother always wins because he actually has body parts, while the older brother only has a head.