Verifying patches means owning the games, which while I would love to own every lewd Steam game, is not practical for me at the moment.
If you have an interest in helping me out with game access, get in touch through the contact page!
There is a patch available, but it has to be bought from the FAKKU website. On top of this, there's some major issues with the patch, which have been around for a while and don't seem to be getting resolved. As such, on the Fuwa Novel forums user Heliosaurus has created a Maitetsu 18+ Release Restoration Patch, and user HoplessHiro is working on a Maitetsu 18+ Demosaic Patch.
Patch download: https://store.fakku.net/products/maitetsu-18-dlc
Steam store: https://store.steampowered.com/app/714800