Xenon ~Mugen no Shitai~

Kouji, a Japanese high school student, experiences strange, recurrent life-like dreams. He finds himself in a space station inhabited by beautiful young women. As he tries to explore the dream realm he wakes up. His teacher, intrigued by his account of the bizarre adventure, urges him to travel back to the space station in his dream and report his discoveries to her. Eventually Kouji realizes that his dream and reality are tightly connected, and finds himself compelled to avert a grave danger.

[From Mobygames]