Chapter 1 is available as a free download:

Wet Night

Yuri no Yume is a plot-centric lesbian hentai science fiction romance.

All episodes are available to HentaiSenshi Arcade members upon completion.

In Wet Night, the second episode of Yuri no Yume, the two girls return to their dorm only to learn that someone has been spying on their trysts...

Purchase the full version through DLSite (Windows only, download the patch for Linux and Mac support.)

Demo download (free): Windows, Linux, Mac.

Uncensor patch to remove mosaic (free download for full version)
Mac and Linux support patches for DLSite version

Episode 1

Full version download for members: Windows, Linux, Mac

Full version purchase through DLSite: Windows only (Note, as DLsite is a Japanese company, the DLsite version has mosaic. Non-DLsite versions do not have mosaic.)
Through BMT Micro: Windows, Mac, Linux.

System requirements:
The Windows version runs on Windows 98/2000/XP/Vista. It also works on Wine. It has not been tested on WinMe.
The Mac version runs on MacOS X 10.4 or higher, on both PPC and Intel processors.
The Linux versions run on x86 and amd64 Linux.