10/10
I'm only giving out two 10's and this is one of them. It's not in my top 2 cases, but that's solely because the stakes for the overall plot are nonexistent and it doesn't hit as hard. But while the other case I'm giving a 10 to is maybe the most important case to all the characters and is just about perfect, this case is one of the least important cases to the characters..... and is absolutely perfect.
There's a good-sized cast filled with new characters, and all of them are really cool and unique to talk to; none of them are remotely like any other character in the series. Because of the scope of everything, it allows for a ton of misdirect to keep everyone guessing the entire time. Hell, going into the final trial day, there are TWO murderer twists still to pop up.
This is the best version of Pearl we ever get, Blackquill plays into everything wonderfully, and tons of stuff in this case is just CLASSIC Phoenix Wright. The cutscenes are great, including the songs, which are just adorable.
The villain transformation is the best in the series, and his motivations are totally believable. I can't hear the Allegro cross examination music for DD without thinking of "The Dissing of Phoenix Wright". Whereas a bunch of murder plots in the series are ridiculous for the sake of being ridiculous, this "murder" is a spur-of-the-moment thing that doesn't even end up that complicated, and it's just a matter of everything else getting convoluted by chance, and it foreshadows so much of it right in your face, which is fantastic. And the twists aren't even done by the time the trial is over, it still has the other aquarium to throw at you!
I love this case, and the more I talk about it, the more I can see me talking myself into it being my absolute favorite case, even above the grand finales.