Portopia Renzoku Satsujin Jiken (The Portopia Serial Murder Case), is an adventure game that was created single-handedly by Yuji Horii and was initially published in Japan by Enix on cassette tapes for the NEC PC-6001 computer in June 1983. The title was later ported to several other Japanese computers but obtained mainstream success with the Famicom version developed by Chunsoft that was released on November 29, 1985. A remake of Portopia was again created by Chunsoft in 2001 that was released for Japanese mobile phones and featured completely redone artwork as well as a newly added save function. The game is the first entry in the Yuji Horii Mysteries trilogy which was followed by Hokkaidou Rensa Satsujin: Ohotsuku ni Kiyu!! in 1984 and Karuizawa Yuukai Annai in 1985.
The game is an investigative adventure title in which the player must solve a murder mystery by searching for clues, exploring different areas, interacting with characters, and solving item-based puzzles all using the game's text parser or the verb window in the console release. The title allows for open-ended exploration where the player can solve the case in a multitude of ways and where their choices can effect the game's non-linear design. Environments are interactive, with the player being able to take out a magnifying glass to examine something or a hammer to hit an object. The game also lacks any kind of fail state and contains several alternate endings depending on who the player decides to accuse of murder. Portopia Renzoku Satsujin Jiken, especially its Famicom port, was received positively in Japan where it was an influential title that defined the adventure game genre. In addition to eventually paving the way for the seminal Dragon Quest series with its implementation of a cursor-based menu system, the title also inspired many future game designers such as Hideo Kojima and Eiji Aonuma.
Kouzou Yamakawa, the president of the Loan and Savings Company, was found dead inside his mansion. A detective and his assistant arrive at the scene for further investigation. The player must resolve the mystery of a murder by searching for clues, interacting with characters, and solving item-based puzzles.