The bus driver is heard saying that they “do this every week.”
“And I don’t think there’s any problem,” they are heard saying to the parents before driving away.
Japanese Lolita fashion is pretty distanced from from Nabokov's original conception. If this person is just dressing in that fashion, and put the sign in reference to that, I could almost understand it, and concede there might not have been anything predatory in nature intended.
But if you're a Westerner, you should be pretty damn aware of how people might interpret it on a bus meant to transport children. Like how dumb can you be?