This seems not to bother Japanese fans who understand that the model's details are a role. Secondly, it can be seen as part of a Japanese tradition of developing roles within roles, this can be seen in the behaviour of the masked Geisha and in Kabuki theatre. It can also be associated with ideas that lie deeper within Japanese culture: Firstly, the idealisation of youth which is reflected in such things as 'cutesie' adult fashions and the portrayal by women of themselves (in terms of dress and manner) as younger than they are. For a fuller understanding of both role play and the idealisation of youth in Japanese media and culture it is worth reading articles by Dr Sharon Kinsella, referenced below.