I'd assume that the "target demographic" would probably be the same as for H!P which are (based on my experiences) kids, teenage/young adult females, some questionable middle-aged men, and horny teenage/young adult males. XD
But right now, since they're going through their "prime" the audience can pretty much be anyone including a lot of casuals who usually aren't in to this stuff just like with Momosu back in the day.
Oh and the single has sold 680,242 so far. In just several hours it could be the #1 yearly... and it would have only taken 3 days.