I think Atelier Choice/ アトリエちょいす generally has peeing content in their rpgs so it could be something that they do. NupuryuNet seems like the one in charge of coding the game but feel free to correct me if I"m wrong.I went back a few posts on the ci-en since i don't generally read each post, and lurk more for info to get posted here...
Despite not having any interest in peeing stuff, the fact that they've specifically gone to the effort to have the one girl's ass deform around the toilet seat really makes me excited for the future of this.