I searched for it on a whim on Cabos after hearing about it. I'm on ep 2 now.
I think it's the parents and teachers fault. They spend so much time keeping the kids in this fake world of school and study and schedules and after-school snacks without teaching them stuff they actually need to know, looking around in the real world, real Japanese society the way it is and giving them the tools they need. Sure, she is a kid and she will make stupid choices regardless, but maybe if she was taught how babies are made (and the subsequent education about how to use a condom), she would have known how to prevent it instead of going "zOMG! There's one in my tummy????"