First off, Satomi lost her "normal" status the second she witnessed the Jack battle. Early on, I think Eve said that those exposed to a strong aura (the kind people of that caliber release in combat) tend to awaken. They don't become pages, they just can see things that are really there rather than what they assume should be there. She assumed that was the cause of Ben's awakening, but it seems his family may be tied to that status instead.
As for the hiding in plain site thing, I think it's the Discwold phenomena again. On the Disc, people don't see things like Death (among other things) because their brains refuse to admit it. This act of mental defiance of facts is so pervasive that he can sit down at a bar, converse casually with his fellow drinkers and the bartender, pay and leave, and afterwards people can only describe him as wearing black and being rather... thin... (one might even say "skeletal")
Whether it's a spiritual cause, simple does-not-compute denial, or an active "perception filter" that is placed on pages to protect everyone involved, nobody who isn't awakened can see the horns or the floating eyes or the fin-like ears. There brains just never look twice, because there's clearly nothing to see, right?
All told, however, it's standard Shonen rules: the real world exists, the world of monsters exists, the two aren't as separate as everyone assumes. The world is like that because the world is a shonen-style setting and that really is all there has to be about it. This also explains gravity-defying hair, ready acceptance of preposterous revelations, and virtual immortality as long as you can avoid dramatic memories of your past while suffering life threatening injuries.