Had a lot of trouble finding this, so for anyone looking for the Ranni the Witch hidden render.
BEWARE, THIS COMMENT DOES INCLUDE SPOILERS!!!!!!
When talking to Alyssa, a few line of dialogue after the option to invite her to your place - Immediately after she holds up her switch console, you will see some hanging garden cubes or whatever they are called in the background. Ranni the witch is sitting on one of them (This is before the makeout/foreplay scene)