An instalment in Human's Twilight Syndrome series, the game was directed and co-written by Suda, and mixes visual novel elements with a horror setting. It would be Suda's final game for Human before he left to found Grasshopper Manufacture in 1998 – but it never got released outside of Japan.
Thankfully, it looks like Suda51 fans might finally be getting the chance to play Moonlight Syndrome in English. Translator @GriffithVIII has posted images of the game running on real hardware in English.
Hopefully, it won't be long before the translation patch is released and we can finally experience this PS1 horror title in our native language.