Number 48

ナンバー48, Ani, (兄), Otouto (弟), The Slicer Brothers
The Slicer Brothers are a pair of serial killers who become one of the guardians of Laboratory 5 under the joint alias of Number 48. They had their souls bound to a single suit of armor by way of a pair of blood runes one in the helm and one in the armors neck piece and were assigned to kill any intruders at the laboratory.