One of the most popular and influential games for the visual novel genre in the 1990s was The Portopia Serial Murder Case. If you haven't heard of it, you're not alone, as the game was not released outside of Japan. The only versions of the game available in the English language are translations made by fans.
Square Enix is seemingly interested in the title and has recently filed a trademark for The Portopia Serial Murder Case. The trademark application was filed on November 10 and made public a few days ago. The trademark was filed under Class 9 which includes use for "machinery and equipment including commercial video game machine software, programs, and virtual reality game software."
The Portopia Serial Murder Case was developed by Enix and released in 1983 on the PC-6001, and has since been ported to other platforms. The game was designed by Yuji Horii, creator of the Dragon Quest series.
The action-adventure visual novel revolved around the death of the president of a bank. The police were sent to investigate the mystery and the player is assigned as the detective on the case. The player travels around several locations to interact with and interview characters who may shed light on the mystery.