He wants to enjoy and get to know this world better, so he wishes to be the age to go to high school and learn more easy, have a more magical body, so that the 3 are more united than they are.
The 3 shrink, until they have the height of a teenager or less, their bodies lose weight, they lose muscle, see that your hair grows, cat ears grow on top, you feel that the structure of your face changes, the fat and muscles of your belly are they leave it thinner, in your chest you grow small breasts, so you feel how your body becomes softer, fragile and feminine ending with your crotch, then a tail grows at the end of your back, then your hair is combed in pigtails , your shirt changes to a long red and white tunic, with a strange style and your pants becomes a skirt.
You see your friends and the same thing happened to them, they are equal girls, only with different clothes, they start talking to each other what happened, when you see that the house changed, now if it seems more magical, and more feminine, realize that they are sisters triplets catgirls, are 14 years old, go to a magical high school, as they know more about their new lives, they start to stop caring about wanting to return to normal or being guys, so decide to stay like a test time, enjoying the experience of being a teen catgirls, strangely even the cat change, now is a small dragon, now you get along better, you like this more as a pet, and he seems to like your new look more