Marry My Nemesis - Chapter 3

I can already tell that ML loved her in the first love and that he was being bullied by others and she most likely showed him kindness which what made him fall in love with her.
The reason why he killed people associated to her (some members of the family) is because they were poisoning her which is how she died. Such a cliché story.
None the less, I will read it until I get bored of already knowing everything xD