The 5th episode of
Gushing Over Magical Girls has a part with shrinking in it...it isn't much, but it's a series that focuses on the villians, the Enormita, torturing the magical girls, Tres Magia, with various mature themes.
This episode introduces a 3rd member of the villainess team, Neroalice aka Korisu Morino, who's Alice in Wonderland-like outfit gives her the power to manipulate toys in various ways, such as trapping victims in doll houses or making stuffed toys giant. While the episode doesn't explore the shrinking fetish yet, it was hinted in the final moments of the episode, when Kiwi asked Korisu to make Utena pretend she's a baby (shrinking involved, of course) but it was backfired when Korisu shrank Utena into a doll prison.
Here's a couple shots, which are mostly perspective shots, but it gets the hint.
And yes, this series is erotic as fuck with a bunch of scenes of fetishes like breastfeeding and the hentai trope of tentacles.
The episode is on HIDIVE for $5/month.
https://www.hidive.com/stream/gushing-o ... ls/s01e005
Here's the screencaps of the episode.