Ayu in Fashion Magazines

[Uemarasan]

I was just wondering, since Ayu appears in so many Japanese fashion magazines, why hasn't she done much work for Non-no? I mean, she's graced the cover of Vivi and Cawaii (both very popular magazines) so many times, but I don't think I've seen her on the cover of Non-no. Does she have an exclusive contract for magazines? Is there a rivalry between Non-no and Vivi? Please correct me if I'm mistaken! Thanks in advance!