Both stories aren't realistic. If you aren't realistic, there's no correlation between decisions and results, which makes the show a waste of time, like watching an acid trip. At that point you may as well just have the acid trip yourselves.
In Masamune-kun, the guy has already saved this girl from death twice, both times by miraculously appearing at the exact moment she was in sudden grave peril and forestalling it. The odds that a random Japanese high school girl would be run over by a car or attacked by a crazed stalker are essentially zero already. For it to happen to the same girl twice is even less likely. And then for him to appear just in time to save her both times is ludicrously unlikely. If that's what it takes for a girl to fall in love with a guy, then just give up. You're just saying that no romance can possibly happen this side of heaven. A romantic comedy is supposed to be a simulation of romance that we can dream of and enjoy vicariously. When you create an unrealistic situation in order to spur the romance forward, you've lost your entire audience, because there's no way they can mirror the events displayed, so no vicarious enjoyment is possible. Only the bitter despair is left that it would take a miracle for a boy and a girl to ever get together.
It is more likely that a bunch of whirling atoms would spontaneously quantum tunnel into a complete, working school bus than Masamune-kun could have charmed this girl, and yet we're supposed to take this show seriously? I don't think so.
Meanwhile, Chaos;Child describes a series of gruesome, grotesque crimes that are so unusual and so aberrant that, in fact, they have never happened in human history. When you're spending all day imagining up the most sickening, absurd, surreal crime scenes imaginable, you have fully detached from Planet Earth. This is no longer about a mystery, or a crime, it's just about shock tactics and gore for gore's sake. When you start delighting in the worst conceivable tortures this world affords for potential crime victims, rather than being paid as a storyteller, I think the police should just go ahead and lock you up as a preventative measure. This is well beyond the needs of the story proper and has gone into full scale psychopathy. Take the gruesomeness out of this story and all that's left is a club and a family that doesn't get along. In other words, it's just a pile of garbage masked by the stench of blood. I hoped for more from this show as the sequel to Chaos;Head, which was at least watchable, but nope. Not only does Chaos;Child suck, it's dragged Chaos;Head down with it, as I can no longer call Chaos;Head good if I can't watch its own continuation any further. So it goes.