X_x wtf? Other people seem to like it but I think it's not good for someone her age
I think you forgot that this was produced in Japan 
I will never get used to that "underage girls are hawt" thing
imo I find it awkward when H!P girls do suggestive poses under age 18, in bikini shots or in whatever the heck Koharu is wearing in that picture. maybe it's just me lol
For those growing up in a more Western society for example, of course it's not something that's particularly easy to adjust to. But hey, in Japan it's normal, so they go on with it

Also, Koharu's expressed she prefers the 'cool' image over the 'cute', and even though she has a lot of fun portraying Kirarin and does it flawlessly, you can see she has equally as much fun (if not more) when doing more mature things. I'm sure she had a blast doing this PB!
And man, I see girls younger than 16 or just a bit older these days wearing less than that black outfit, so it's nothing scandalous to me

I agree that most people are just really surprised by the mere fact that it's such a mature shot since we're so used to her being this spazzy, dorky girl.