Released on November 26, 1998, for the PlayStation, the Serial Experiments Lain game consists mostly of pieces of information collected in a random order that allow the player to piece together Lain Iwakura's story.
There is guidebook for this game titled Serial Experiments Lain Official Guide.
The player controls a Lain avatar and navigates a hierarchical system of computer files. The events of the game follow Iwakura Lain and her psychiatrist Yonera Touko. The following is a rough summary of the game's events as related by Keisuke Shindo. 
- Lain (11) begins to visit Touko (27) because of hallucinations.
- Touko teaches Lain about psychopathology.
- Lain has a friend named Kyoko, who she has a falling out with going into junior high school.
- Lain enters junior high, gaining a friend named Misato and an interest in computers and networks.
- Lain's father disappears under mysterious circumstances, and she programs an AI into a robotic replacement of him.
- After 3 years of counseling, Touko thinks Lain has no more problems.
- Touko begins to diagnose Lain again after finding out from classmates of Lain that Misato does not actually exist.
- Lain programs her father into the Wired and destroys its robotic body, subsequently beginning to program her own personality into the Wired.
- Touko experiences frustration over her lack of mobility at work. Her boss kills himself.
- Touko experiences relationship difficulties, getting dumped by two men in succession.
- Touko becomes emotionally unstable and Lain begins to diagnose her.
- Lain meets her Wired entity and kills her physical self.
- Lain appears before Touko and kills her, absorbing her personality into the wired.
Lain Iwakura An apparently ordinary girl with a highly introverted nature and low self-esteem. At age 11, she begins to see and hear hallucinations, most prominently a double of herself. As a result, she sees a therapist at Tachibana General Laboratories. Lain also proves to be adept at psychology and computer science. Most of all, she is unbearably lonely.
Touko Yonera Recently graduated from an American university, Touko serves as Lain's counselor and psychiatrist. She is a new employee at Tachibana Research Center, and Lain is her very first client, establishing quite a good relationship with her.
Makino Shin'ichirou An ordinary office worker who encounters Lain online. Impressed with her abilities, he provides news, data and computer parts for her.
Tomo A boy in Lain's elementary school class that Lain has a crush on.
Kyoko A girl in Lain's elementary school class that Lain is somewhat friendly with, who treats Lain like a younger sister.
Mayu A friend of Kyoko's.
Kaori A girl in Lain's elementary school class that tries to be friendly with everyone.
Yasuo Iwakura Lain's father. He and Lain are very close and he treats Lain very kindly, often buying her presents. He is a businessman that occasionally needs to travel.
Miho Iwakura Lain's mother. She and Lain are on slightly less good terms, and she is a bit harder on Lain than her father. She still treats Lain very well and looks after her when she needs help. She is a housewife.
Misato Lain's (imaginary) friend in her middle school class. Getting along extremely well, Lain and her do all sorts of things together, at least in Lain's memory. Misato is an ideal girl, able to play the violin beautifully, paint exquisitely, and is also very beautiful and elegant.
Harumi Touko's longtime friend. She rather abruptly gets married.
Kanako Touko's longtime friend. She's a hardworking woman trying to become a publisher.
Takeshi Touko's boyfriend, met while studying abroad. He works at Tachibana General Laboratories alongside Touko. Their relationship is very platonic.
Yoshida Touko's other lover. He works at an exercise equipment manufacturing company that visits Tachibana General Laboratories from time to time. He is popular with women.
Professor Takashima Touko's boss. A well-meaning man that often dumps chores on Touko, impeding her research. Touko hates him.
Mr. Rabbit A friend that Lain made online. He teaches her how to hack.
Shock Spammer A malevolent user online that sends encrypted shock images to Lain's inbox, such as images of a dead infant and a dead woman.
Progenetis Lain's father. After the disappearance of Father, Lain begins to make artificial replacements of her friends and family, starting with Father.
Bike-chan A stuffed toy dog that allegedly has been Lain since her birth. Lain seems to view it as a friend.
The Other Self A hallucination of another Lain that appears nude. She is the reason that Lain starts seeing Touko.
CLN-1 An unnamed woman in a school-girl's uniform that shoots her boyfriend in public.
The game's interface is designed to be somewhat similar to a database, apparently called the "life instinct function" or "lif", which appears to be located on a server at Tachibana General Laboratories. The name of the database could hint that it is serving the purpose of keeping lain alive somehow. The database is divided into two Sites: Site A and Site B. Site B is locked when the player begins the game, and can only be unlocked by finding updates hidden in the files. Each file in the site contains an invisible version number. The version of the player's in-game media player must be greater than or equal to that number in order to play the file. The media player can be updated by finding various upgrades hidden in the files.
Located within the database are several different filetypes:
- Lda, standing for lain's_DIARY in game, is a collection of 237 diary entries written by Lain over the course of roughly three years. The diary was given to Lain by Touko early into the counseling sessions as a place to confide her often negative and personal feelings. Interestingly, there is an image included in the game of Touko giving Lain a physical book, but the diaries themselves have evidence to show that the diaries are electronic. It is possible that Lain writes the diaries and then records herself reading them.
- Tda, or TOUKO'S_DIARY, is a collection of 92 diary entries written by Yonera Touko over the course of roughly two years.
- Cou, or COUNSELING_REC. is a collection of 53 recordings of counseling sessions between Lain and Touko. While the earlier sessions had Touko acting as a counselor to Lain, in the final recordings the roles are reversed after Touko becomes unstable. Lain acts as a counselor using her wide knowledge of psychology from independent study.
- Dia, or DIAGNOSIS_CLN## is a collection of 48 diagnoses by either Touko or Lain regarding their patient's behavior and actions to be taken as a result. Touko's recordings bear the designation CLN_01 (referring to Lain) and Lain's bear the designation CLN_00 (referring to Touko). The final recording is done by both.
- TaK is a series of 181 recordings of a single sentence each by either Lain or Touko, seemingly addressing the player. These sentences are often random questions. Unlike other filetypes, which are mostly presented in chronological order by level number, these files are presented in two apparently parallel chronologies, one consisting of the recordings by Lain (TaK001-TaK121) and the other by Touko (TaK122-181). There is no label for this filetype, but the Serial Experiments Lain Official Guide calls them "Talk" files.
- Ekm is a series of 6 recordings of conversations between Lain and Kyoko. The label for this filetype is "DATA of CLN01", but the Serial Experiments Lain Official Guide calls these files "Extra Kyoko's Memory". These files only exist on Site A.
- Ere, or RESEARCH_"Ky" and RESEARCH_"Ka" is a series of 10 interviews between Touko and some of Lain's classmates regarding Lain. The Serial Experiments Official Guide calls these files "Extra Research". These files only exist on Site B.
- Eda or RESEARCH_"Ma" is a series of 4 counseling sessions between Makino and possibly Professor Takashima, and 1 news report. The fifth file has the designation NEWS_SHOW. The Serial Experiments Lain Official Guide calls these files "Extra Data". These files only exist on Site B.
- Sskn or SaiSei-kun is a collection of freeware upgrade apps for the game's movie playing tool. Each successive update unlocks more content. There are seven upgrades available. The designation for these files is "mT up-date App."
- P2- or POLY-TAN PARTS are pieces of a virtual bear model named Poly-tan. Collecting all parts unlocks some files, according to the Serial Experiments Lain Official Guide. There are 6 in all, all of which are located on Site A.
- GaTE is a series of network applications that are needed to proceed from Site A to Site B. There are 4 in all.
- Dc1, or DATA of CLN## is a series of 57 animated video files, mostly of Lain. While the numbers do go up to 058, Dc1029 is missing. Unlike the other filetypes, these files are presented in mostly random order, Site A containing the first 28 and Site B containing the latter 29. Each video file has its own name. Interestingly, the name "drive" is used twice. It is unknown who filmed these files or for what purpose, or whether there was even a cameraman at all. While some files have a distinctly handheld look to them or are clearly for the purpose of filming a counseling session, others are far more unusual; some appear to be hidden cameras, others appear to be professionally edited to show a series of events from a certain angle, and still others appear to be impossible or difficult shots, like aerial shots or shots of Lain in a bathroom mirror with no visible camera behind her. The CLN number, or client number, varies occasionally, but for most of the files is CLN01, or Lain. A few files in Site B use the designations CLN00 (Touko) or CLN-1 (a seemingly unnamed woman). The missing file, Dc1029, appears to be located between Site A and B, and its contents are located in the short manga "The Nightmare of Fabrication". The Serial Experiments Lain Official Guide calls these files "Dcl".
- Env or network voices? is a series of 12 files that contain nothing but static and assorted voices. The server data for all these files are corrupted. These files are extra content and are not part of the regular game. All of these files are located on Site A's Level 0.
- Xv0 is a collection of unused video clips. These files are extra content and are not part of the regular game.
- Xa is a collection of miscellaneous audio. Most of these files contain Touko in an apparent state of distress, though the first and last files contain Lain's voice. These files are extra content and are not part of the regular game.
Connections between the game and the anime
This game explains many elements in the anime that are taken for granted or left unexplained. It can be considered an alternate timeline to the anime, perhaps one where Lain is incarnated into a different environment.
- Lain's haircut
In the game, it is revealed that Lain cut her own hair. The longer lock of hair where she clips her hairclip is meant to prevent something that "enters from the right" from "going out through the left". Not much is known about the context of this statement (at least to the English-speaking fandom), but it has been theorised that Lain's hairstyle wards off demons or prevents her memories from disappearing.
- The chip from Layer 09
- Shared themes
Access to the fan translation at laingame.net
As the videogame has never been officially translated, a team of fans has fan translated the entire game in English and made the nodes easily browsable. Project began in 2008 and the translation was released in 2014.
A long time passed after a team of volunteers decided to remake the game from the ground up using web technologies (React, three.js, WebGL) making the whole game playable in the web browser. Work on lainTSX started solo by ad044 since August 2020, and on 13 September 2020 help was gathered from community. Decision to recreate the game in the browser made the translation, especially the integration of the subtitles easier, and gave the opportunity to smooth the gameplay and the animation using a better framerate and overall timing.