The novel was first published in a shounen ai magazine Shousetsu June [issues: 22 (XII '86) – 27 (X '87)].
In 1990, slightly reedited by the author, it was published as a hard-cover book.
From January 2001 to July 2009 it was being released again by Seibido Shuppan (known also as Crystal Bunko). This time it was significantly reworked and made into a series of several volumes:
Vol. 1: Stranger
Vol. 2: Destiny
Vol. 3: Nightmare
Vol. 4: Suggestion
Vol. 5: Darkness
Vol. 6: Metamorphose
Which is not the end of the novel.
In 2009 the copyrights have been taken over by another publisher, Tokuma Shoten, who started to release the novel from anew. The first four volumes cover the content of all six published by Seibido Shuppan. There is a total of six volumes, which make the whole novel this time. The last volume came out in January 2010.
The six volumes given to us by Crystal Bunko have been translated into Englished and published by DMP (Digital Manga Publishing). There is also an ongoing fan translation that comes from the hard-cover book edition. Here are the links to the English chapters (stored on the translator's site).
Japanese to Spanish translation: Shabriri
Spanish to English translation: Shiromori & San-chan
Japanese to English translation: Ai-chan
For more you will have to wait. Or you can read the synopsis below.
The synopsis is divided into paragraphs by scenes or events. It was made from the second edition of the novel (Polish translation). I tried to write it in a way so that you could understand the story even without watching the OVA or reading the script first. If a scene has an equivalent in the anime or in the drama, I usually mention it.
When it comes to the background info, I've put the explanations exactly where they are in the book. I explained everything I considered necessary to follow the plot, especially things that aren't mentioned in the anime or are different than in the anime.
There are many "side tracks" in the novel, like timeline jumps or background info. I put them into separate, but indented pafagraphs so that they could be easily distinguished. There are some places where the author doesn't make it clear that she has just made a jump. I left it unexplained as well to make the synopsis as appealing as possible. Don't blame me. ;-)