Four Arm Mutant

Immediately after that, four bodies simultaneously spliced into eight bodies as black blood and reddish brown soft tissues scattered around the floor. 

The four mutated human suddenly felt their vision spin. In a daze they inspected themselves only to realise that they had been separated from their lower halves.

The female mutant did not quickly die, as their lower body was still running forwards. 

She looked at their separated bodies in disbelief. How.. How is that even possible? Don't tell me that the institute sent a senior student in to deal with them?

They had attacked the girl previously and knew that the girl was definitely not powerful enough to kill them in single strike no matter which tool or gadget she used, it was impossible to kill them all in as single strike. 

Which only left the possibility that she had been toying with them since the very beginning.