The reason why the rare candy is rare is because of her eating so much of it to make it hard to find and its really a placebo effect for the sugar in it makes her believe herself stronger when really its just the sugar rush effect that she seriously craves but finds the MC cum better and finally makes a emotional connection to others and she realizes the candy never did anything to her but some cavity's. Once she stops looking for the candy it just regular candy with ALOT of sugar not called rare candy anymore.