I finished The Caligula Effect: Overdose last night. Overall, I would say the game is... enjoyable.
What I can definitely say to be good is the music, especially the various themes for the villains and boss battles. Makes sense, considering music is important to the plot: the songs playing in the dungeons and areas are supposed to be played all the time to brainwash people into listening to Myu and giving her more power. And I can say it definitely works because even if the themes are technically short, they are neat to listen to, and end up staying in your head, just like for the characters in the games. Especially the remix of the theme done for the boss battle against the Musicians. And the remixes of the remixes in the final dungeon.

Speaking of dungeons... they aren't that great. They remind me of the P3/P4 dungeons. Go to an area, run around to fill out the map. Except the floor designs aren't randomized. But the dungeons are basically the same: different design, different music, but the overall gimmick is the same. Do this to unlock ways to go further on, fight Musician, done. As I said, the music for these areas is pretty neat, but the gameplay of it is just not that entertaining.

The plot is okay. I was wrong about the identity of the Big Bad Musician. It was clear there was a connection to Shogo, though I based it on appearance. Still wrong in the general sense of their identity, but okay. Some revelations don't feel... well done? Though it might be because I am looking at it from someone who feels the game dragged on a little too long. The revelations start around the penultimate dungeon's end, and some stuff gets mentioned that wasn't before, so... feels kinda disconnected.

I know that Overdose specifically gives you an option to view another side of the story by going through a door the Musicians offer you... but I was surprised it was given as a one-time choice after the second dungeon. I didn't go for it on this first playthrough. But I have read what it's about. (It basically allows you to create a 'bad ending') Will do it on a second playthrough - will have to do a second playthrough, anyway, because there's a trophy for going through the game as the female and male protagonist. (Female protagonist option exclusive to Overdose)

Sidequests... suck. There are 524 NPCs in the game who have sidequests. The sidequests are dealing with that person's Trauma. You get many copy quests, and you can only take care of one at a time. Even if you have multiple NPCs whose Trauma is 'Alexithymia', which is resolved by defeating 20 enemies with the NPC in your party, you cannot resolve them all at once. You cannot take on several of those quests at once, then resolve them at once. You can have multiple NPCs in your party, sure, but the sidequest only gets done for one of them...
And now you do that multiple times because copy quests.
Many also involve finding a certain stationary NPC... to which I have to say, it would be really nice if the damn game somehow marked these NPCs on your map! But nope. They don't get marked, so you just have to remember where these NPCs are. The quest gives you a hint where that NPC is located (like in Papiko or the Construction Site), but it's up to you to either find them or remember where they are. And some areas are 'big' or have round-about ways on the map, so you run around a lot.
There's also extra challenges based on 'Words' that enemies may drop... they drop them very, very, VERY rarely! In my entire playthrough, I managed to get ONE word dropped. Fortunately, you don't actually have to obtain them to unlock the doors for the extra challenges, you just need to insert the words. Thank you, internet, for having a list of these passwords!

Sidenote, enemies do not disappear from a dungeon you already cleared. I can understand why, given the extra challenge word drop thing above, but it's kinda ridiculous to have Level 1 enemies still wandering around in the school. Can be avoided, but I'd prefer for it to not be the case.

Enjoyable game, definitely. Bit too long for my taste - especially since it's basically a wild goose chase of "Catch up to Myu and make her let you go home" over and over. Glad I got it, though I'm not sure if 60€ is an appropriate price for this game in new condition. I'm taking a break from it, and will eventually return to continue sidequesting or doing the second playthrough, including the alternate POV. Especially since cleared save files let you carry over your Level AND your Causality Link (Sidequest) status. And loading the file puts you just before the final battle, so you don't have to worry about having to wait until the later dungeons to finish up those sidequests needing them unlocked.

Remember the older days? Where you didn't have New Game +? Or where New Game + loads meant you were thrown into the Grade Shop or into a new playthrough entirely, so you better have a savefile of before fighting the final battle, so you wouldn't lose opportunities? Yeah... kinda miss those at times...

---