I think its an excellent idea that you have different TOS for different sections. It already looks as if there are because there are certainly images of Aiko in the MP that could nver be looked on as over 18. 
Of course very site can have its own TOS no-one denies that - but I sometimes wonder if the TOS as they are interpreted are actually legal or if someone wanted to if they could be challenged in a court of law. (I am not just talking about this site's TOS here I am talking in general) 
I wonder also if this is actually classed as a "private site"  - its not someones website where they post things for their own enjoymnen. Its a business. It makes money and it pays wages. 
A shop in the high streeet can be privately owned - but it still has to follow laws laid out for commerce. 
Its like when you go in a store and the shop has something saying what its exchange laws are. If those rules aren't legal they can't be implemented. 
That's why I would have thought it better to ban people from the forums or from uploading images but not also ban them from purchasing items in the store.