You already can buy everything you need at the shop and it wouldn't make much sense to make more shopkeeper characters (considering that every character in game has her own unique role), so these shops likely exist purely for the entourage. Medals (I assume you mean achievements medals) are all fully unlockable. To see Aunt in swimsuit you should be swimming when the timer reaches 18:00.i think the game is incomplete, it was probably meant to be a lot more, there are way to many rooms, there are some other shops that are closed, there are extra medals, and i saw a glitch where the aunt was in swim suit when calling mc back for dinner