Hey guys, I found an AR some time ago in a manga called Akuma no Memumemu-chan, which I completely forgot to upload until now... ^^"
The manga, if I'm not mistaken, follows around a high-school boy and his family and friends watching over a young demon boy named Memumemu, hence the name. Chapter 23 features AR as the characters drink milk that causes them to rejuvenate. There's very little in the way of process, but it's cute and leaves them in baggy clothes. Two girls and a boy turn into children, the boy's mother turns into a cute teen, and Memumemu turns into a baby.
The manga can be found on the website Shonen Jump + for free:
https://shonenjumpplus.com/episode/13932016480028899974