Never had I seen a piece of Lupin fan media that felt like it spoke to the specific type of fan that I am, down to every single detail and nitpick I had about the franchise.
First things first, the art and music are gorgeous. I'm someone who just puts on Yuji Ohno music to vibe and I can 100% see myself putting on this game's remixes, they're just that good. The art is very pretty as well, there are a few iffy expressions, but the presentation is spot-on, ESPECIALLY with how the designs change as the chapters go by and we see the characters in different stages of their lives. I'm split on that decision, though: one part of my brain would have loved a consistent design, especially when it comes to the shape of their faces, but I feel like the change in designs ends up working out very well in the end.
Secondly, every character feels very in-character. The main barrier between me and ship fanfic content is that a lot of them don't seem to get the characters. But this one does, and VERY well. The progression of Lupin's inner monologue and the kinds of things he either says or thinks about saying for most of the game are very true to Lupin. Every time a character talks about what they're like or what they think I sat there thinking "YEAH, THEY GET IT." The only two exceptions, where I felt like the characters where a bit off (though not that much) are moments in Chapter 2, one where Jigen delivers a long monologue and another where something pivotal to the plot happens, not gonna say what it is in case somebody who hasn't played it is reading this, but I think it felt a little bit more like stereotypical fanfiction when contrasted with the extraordinary attention to every detail of the characters' personalities that is present in every other moment. As for the other part, I get it, the Lupin Gang is full of characters who say more with what they do than with what words come out of their mouths, so there was bound to be some awkwardness due to the medium, even if just a little bit...
---Spoilers for the game, Part 4 and Part 5, in case you haven't finished any of them---
HOWEVER I just fucking adore the twist at the end, where the game mechanics don't seem to work as usual and Lupin just breaks the entire interface. Not only do I love meta fuckery with the UI, NOT ONLY does it beautifully express Lupin's way of acting in a way that only a visual novel can, BUT it also critiques the somewhat shitty and manipulative nature inherent to dating sims of that type while staying within the bounds of Lupin's character. Just incredible. Especially considering that I, the player, by engaging with the mechanics of the VN, got to think like that, to see how my conversation choices affected all the numbers and the like. The whole time I thought "it is a little shitty that I'm going to get the best ending by just saying what will get me the most optimal trust and openness points" but NO, THEY KNEW, THEY FUCKING KNEW, AND I LOVE THAT.
One small gripe that I have before going into one of my favourite parts of this beautiful story is: Chapter 3 takes place after Part 4 of the anime, and I thought that, since Lupin and Fujiko getting married was an important plot point, that the whole wedding with Rebbecca would be brought up. However, it's not bad that it wasn't, and I only really noticed because the rest of the VN is extremely good at using all the little details and bits of Lupin lore.
And finally (but not really, I keep thinking of things to say as I'm writing this), what really made me feel like this VN was made specifically for me, by distilling all of my thoughts and complains about the Lupin franchise, was in Chapter 3 and 4. They took all of the missed potential that Part 5 utterly annihilated and MADE IT WORK. The pirate job, Lupin's failed relationship with Fujiko, how and what he really thinks about his gang, and the question of why Lupin continues to put himself in danger in thefts and heists every time. While Part 5 kinda answers all of those VERY interesting questions with references and a few hand-waves, this fan-made gay ship visual novel actually runs with all of those concepts and makes them into exactly the kind of exploration I wanted to see out of Part 5.
An observation that came into my mind as I was writing this excessively long comment: the issue of Lupin being a manipulator by nature and having to work through his issue of taking his teammates for granted kinda reminds me of the bad Part 2 episodes and the more mediocre TV Specials like Operation: Return The Treasure, where Lupin's worst traits get amplified to the point where his entire deal is manipulating others and pissing off his friends for no reason.
Absolutely stellar work, I never thought I'd enjoy a piece of fanfiction this much, I love every single bit, and I feel like this could stand alone as just good character-driven Lupin.