I read a doujinshi of Jojo's Bizarre Adventure in which a guy finds a magical girl type of wand and he becomes a magical boy. So he becomes a boy. Is there any shota yaoi in which an adult transforms into a kid?

Sayonara, Otoko No Ko is the only one I can think of rn.
This tag might help- https://www.mangaupdates.com/series.html?category=Age+Regression