The game was written, designed, directed, and programmed, by the late Hiroyuki Kanno, with music composed by the late Ryu Umemoto, both of whom passed away in 2011.
Kōji, 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 Kōji realizes that his dream and reality are tightly connected, and finds himself compelled to avert a grave danger.
Xenon is a sci-fi visual novel with horror elements. The player takes control of Kōji by occasionally making decisions, including dialogue choices and choosing locations. The entire game is confined to the space station of Kōji's dream and the high school building of reality. Depending on the player's decisions, the story may branch into different directions, creating alternate versions of Kōji's dream.