Still waters run deep, of course.
Yuno is innocent in the "see no evil" sort of way; that is, she purposefully turns away from doing "bad things" to be a "good girl."
However, with Miyako, bad/good is largely irrelevant. She's innocent in the sense that she sees little beyond her immediate needs and desires.
Of course, a girl who knows what's wrong but refuses to acknowledge it is much cuter than a girl who has no knowledge of such things, mostly because you can make the former blush. And there is very little that's cuter than a furiously blushing girl.