there are two different parts to this:
- is it okay?
sure, she's not underage and whether it's the director of the photobook's decision to do a shot like that, or becomes Mano's decision when she complies, it's perfectly okay for her to do whatever she wants. heck, if she decides to do AV, as long as it's her own decision and she wasn't pushed into it, that's also okay.
- do we like it?
that's up to each person's individual preference.
so for me there were two things i didn't like about it that are quite separate: 1) her styling. the wig is too dark and not a good cut for her, i also don't like the make-up. the outfit is interesting though! i wish it was paired with better hair/make-up. 2) her hands being tied. it's so easy for me to forget about the "leerer" type of fan that pretty much only is into the fandom for the wank material, and even with bikini shots (especially the more innocent photos) i can enjoy looking at pictures without thinking too much about that. but with other more suggestive photos (such as this one and the Koharu one that basically looked like an accidental panty peek, yet it must have been intentional because it was published) i simply don't like to see them and wish the market didn't encourage it.
of course there's nothing i can do about that, it's just that personally i don't much care for those photos. but my opinion on this photo is not good regardless, if she didn't have her hands tied (so let's say for example it was tied in an interesting bow around just ONE hand, which leaves the overall effect intact without the obvious implication) it would be much better, but i also didn't like the styling so i still can't say i'd like the photo anyway.
i guess the styling's not totally related to this conversation, but it is on topic with the thread.

for the record, i also don't much care for the cover photo. her hair is cute and i'm all for cat ears and more interesting wardrobe choices, but i'm starting to get a feel for the style of this PB and i'm not sure i like it. :< maybe in person they look better than in the scans we've gotten? cuz the ones i've seen so far look too dark and LQ, which is part of the intention but i don't think it's coming across in a good way. just looks like they were taken with a cheap camera, or not properly balanced to look good for print.