Actually no! He meant that with the killing her. That's why she tries to please him - to survive. And as the uploader stated "those dreams" are just that.. dreams! that never happened. so there is no childhood friend. And he is this killer that wanted her dead in the begining.. even though she tried to help them.. just because.. and now that she managed to survive that time he does everything to make her suffer for that (threatening to kill her parents, friends, students and husband (and even cut of his finger) forced her to sleep with other men and raped her already multiple times and will do even worse stuff). If you think a person that cares for you and loves you will do stuff like that I am genuinely worried about you!
Damn.
This manga if pretty fucked up but you can see how much he really loves her in his eyes when he looks at her and like he actually cares for her. He only says when I get bored of you and kill you then you'll be free but he just says that so she won't leave him. Like damn . (=・ω・=) but I would recommend you read this also in the novel she births his baby and it had white hair and he also dies and I'm pretty sure he was her childhood friend not the killer.