Fact:
– Mr. M is an unregistered human being
– SM’s birth was only registered 9 years after he was born
– Mr. M has this weird scar on his neck
– SM has scar on his ankle
– SM and mother were locked up for at least 9 years

Theory
– Mr. M also went through similar conditions. Perhaps he was locked up in the same place when he was younger. and his chains were around his neck. Perhaps he was locked up by his parent(s) who had chained him up. Perhaps his mother died so he was never registered as a citizen, suggesting it was an abusive father? Thus he grew up this way and thought this is how you treat people you love…. which is why he locked up the young girl that he saw on her way to/from school.. because he loved her at first sight! and this is his way to express love! sooo… there fore…. he loved SM as well… until SM and mother ran away and thus he believed SM took away his treasure and now seeks to do the same thing to him.