The Little Princess in High Spirits (chapter)

Summary
Momoka visits the Sket Dan, and she and Himeko have a toast to her seiyū success with a bottle of Coke, which turns out to be Chūma's youth potion. The two are reverted to toddler bodies, much to Himeko's delight. Bossun is tasked with babysitting the girls while Chū-san makes a remedy to prevent their bodies from being permanently changed. Himeko causes a lot of trouble and Switch escapes while Chū-san asks Bossun to go buy the ingredients for the remedy.

Bossun ends up taking the girls along and frustrated, sends them to buy ingredients. However, the girls accidentally end up being taken away in a truck, forcing Bossun to go after them. Having suffered a scare, the girls quickly take the remedy back at school...but they end up aging ten years too far.