(Me at least couldn't give a rat's ass about him)
Well Mizuno did not kill anyone to begging with, he had a fight with his brother and ran away from home meanwhile his brother was searching for him and got hit by a car so that's why Mizuno thinks and says that he killed his brother. On the other hand he has twisted personality because he is always compared with his dead brother and bullied by his peers (quite a pitiful sight). Yet he did shoplifting, stole money from his parents and hurt both Kaoru and Haruka...
I said get away with murder as an expression. I know Mizuno didn't kill anyone. I'm just angry that he doesn't get a punishment or anything for being an arse. There are a lot of characters in manga that do unforgivable things (not necessarily murder) yet the main character manages to forgive and even forget. Maybe not a punishment, but this is the kind of person that is better out of your life, yet we see the characters actively seeking to get them into their life's back.
Although I think this story is really good I hate when characters like Mizuno get away with murder. It's like it's just to show us the goodness of the main character when in reality one would be more like Kaoru.