Celinda Reyes’s Reviews > Monster: Perfect Edition, Vol. 1 > Status Update

So I wonder if Nina is actually Johan's twin sister and the reason why he's killing childless couples is because she got adopted after what happens to the twins in the beginning of the story. So now maybe he's trying to find her/punishing people like the couple who adopted her. I guess I'll find out if this is true. Either way loving this manga so far!