This is kind of a sequel to "Butler Boy and Princess Girl".
The game was supposed to have the intro actually explain the mushroom king more with him having dialogue, he is like a magical guardian and without him the forest dies.
The purpose of the curse is for the mushroom forest to grow again, this happens when the Queen has sex; a parasite is released and takes over their bodies, but when she is turned into a soup the parasite dies and the people drink a mushroom soup with medicinal properties.
All of the mushrooms are "alive", they look like that because of how the people treated them and because of evolution, they have faces so people don't eat them, cute mushroom has a bow because the girls of the village give them those as a tradition. Sexy mushroom has breasts to entice men, sad failed and it gets eaten a lot, scary also failed but lashed out.
The curse works the same in all of the endings (yes, it wasn't realized or mentioned for different reasons), the Queen doesn't lose her limbs in the sexy ending because the parasyte doesn't take over her (she wouldn't be able to give it to others if that happened).
Inside the cute ending only the butler gets infected, but they have time to figure out a cure, the Queen is not cured in any of the endings.
Thanks for playing.