Incredibly unrealistic and unhealthy, this person's obsession with her brother is causing problems in her relationships at school but were supposed to pretend there's nothing wrong with it so the plot can be lighthearted. The sister is cute though so eh whatever
But the childhood friend was obsessed with the MC and had feelings for him like a dog, while the MC eventually killed him and took his girl like a scum. I think the title is clever because it could apply to both of them.
Why is smacking someones hand always so dramatic in manga. If someone did that in real life i'd just think their reflexes kicked in and move on with my life.