1983's graphic adventure murder mystery for the PC-6001 is influential in countless ways, but relatively unheard of outside of Japan. After all, it never got an official localization, and despite its Famicom port having a very solid English patch in 2006 by DvD Translations, I'm not sure there was enough of a scene to really spread the word online like there is today.
Like many people, my first real interaction with Portopia was its first ever official English localization: the AI Tech Preview remake that Square-Enix released early 2023. Long story short--it's a mess of a text parser that almost never understands very basic commands, and in my opinion unplayable without spending a long time butting your head against unreasonable constraints. Supposedly they actually removed the Natural Language Processing tech from the public demo for fear of users submitting "unethical replies" which reduced the parser to the disappointment we can play today. Yes, that means they released and branded it as an AI Tech Preview without the tech it's supposed to be previewing. I don't get it either.
So let's just ignore all that. What was the original game like? The original 1983 version actually had a text parser like a text adventure game, but I don't think there's an English version of that. The Famicom port, released in 1985, replaced the parser with a list of commands and sub-commands that you can choose from a menu, but kept Portopia's signature investigation style: cracking a case with very little guidance by directing your subordinate Yasu with a wide variety of commands including inspecting, taking into evidence, questioning people, even hitting uncooperative suspects. There are so many commands that it's easy to forget to do some important ones here and there like ordering Yasu to fact-check an alibi, but that freedom does attempt to ensure that you're thinking about the case rather than trying every option blindly in a menu. That is, until that alibi fact-check you forgot to do before comes back to bite you!
If you play Portopia, you will almost certainly need a guide. In the AI Tech version's case, it's to know what verbs you even have access to (Did you know you can take photos of your suspects in the interrogation room? The game sure won't tell you.) but in the Famicom version, there are pixel hunts hiding crucial evidence. Progression happens secretly as you do seemingly unrelated actions, prompting events like receiving a phone call after returning to the police station only because you found a hidden space in the mansion. Maybe it could feel immersive, but if you get stuck, you'll really be stuck since the path forward won't necessarily be logical beyond doing meaningful actions to "pass time" in the story. There aren't many guides online about this game, but the one I recommend is here as it breaks down what actions you need to do, and what they trigger when you do them: https://retrogamesuperhyper.com/2020/04/12/solving-the-portopia-serial-murder-case/
There's also a disaster of a first-person maze with a really unfair secret towards the end of the game. You're given half a map and the solution involves picking a specific unmarked section of wall in the maze and walking into it until the wall collapses into a secret room. I still don't know if it's even possible to know the solution to this through in-game clues.
So obviously I have a lot of issues with the game's design. Aspects of either version have friction where there shouldn't be. In the Famicom version I shouldn't have to inspect an unmarked corner of a front door to find a ring. In the AI Tech version I shouldn't have to guess what words will make Yasu do what I'm trying to ask him to do.
And yet...I admire Famicom Portopia for what it is, and I can forgive its more unfair aspects that haven't aged well. I think this style of detective game still has a ton of untapped potential despite its already wide influence. The simplification of interactions in most mystery games often leads to the game doing the heavy lifting when it comes to making connections and interrogating people. With a more clear evidence gathering system and progress more tied to player discovery leading to further discoveries instead of time passing, this style could really shine.