can a monster feel?

Katsuki had never been a human. He is a monster the whole while under the guise of human skin - the mangled body on the pavement is the proof of his sin.

The day where Katsuki ceased to be a human, was the day where Deku had taken his advice and took a swan dive off the roof. It was the day where Katsuki finally realised what a monster he has been all the while long. That day, Izuku's heart had almost stopped beating, but it was Katsuki who eventually flat-lined.

Since then, he has continued on his daily life, not living, not breathing, without a single pulse to his name. That day was the day Katsuki ceased to be a human and became a full-fledged monster he always had been.