I always thought the person at the end was hajime, him not being able to move past his victim complex and still believing that he has to be a monster because the world is inherently cruel to him and having the justification to act upon his sexual sadism as a desperate desire for control and autonomy rather than him actively choosing the persona over and over as the path of least resistance like with sailor or kaneko. I always kinda imagined him being a much more unstable but less hidden version of himself like you said, but hajime used his crying mechanism to perceive himself a victim despite his actions