User blog comment:Monkey.D.Me/Fan-Service OVER 9000/@comment-3125914-20121023113730/@comment-3125914-20121024114637

I think it's mainly for boys because the genre shounen also suggests the target audience. Just like shoujo is for young girls, seinen for adult males, josei for adult females and children manga for children. But of course nobody stops girls from reading and liking OP and the same goes for the others as well.