No this game isn't transphobic or fatphobic, if you say this or if someone has told you this then they haven't beaten the game and it shows. Anyway,

Overview
The story of the game is about a bunch of people trapped in a virtual world named Möbius (a maths concept about a one sided shape) by a virtuadoll (virtual idol) named μ. Your character is part of the Go-Home Club, a group of high schoolers who also know the world is fake and want to get out. In your way are the Musicians, a group of people who know the world is fake and want to keep everyone in it. They do this by writing songs for μ to sing, her songs brainwash the residents of Möbius and keep them dependent on it and these songs are used as the dungeon themes.

Characters
When you name your character and choose their gender, you're asked a few questions that make it clear that people forced into Möbius are ones that have experienced terrible things in the real world, be they minor or major. The people you meet in game seem fine when you interact with them but if you take time to increase your affinity with them (haha persona), you can dive deep into their traumas and help them recover.

You increase affinity by beating enemies with your party and doing this unlocks ranks for what is basically social links for each GHC member. There wasn't a single bad social link in the game. Even the worse ones like Naruko who's basically White Girl Syndrome incarnate are entertaining.

The issues the party members have can range from "hm that doesn't seem like that big of an issue" to "wow that guys fucked" and the writing + voice acting manage to portray it in a relatable way. It's nice to watch the characters stop coping over their issues and start making steps to actually fix them.

Something I really loved about the social links (named Character Episodes here) is that unlike Persona 4 and 5, if you say something stupid or jokey during a serious moment, the game will punish you by cancelling the link right there. You can't continue it unless you reload a save or unless you spend big amounts of skill points to fix it. Getting all the way to rank 9 successfully rewards you with a character's Ultimate skill which are usually pretty OP.

Music
Sex incarnate. Chances are if you've seen another Caligula review they've hyped up the music and let me tell you, it really deserves the hype. The OST itself is okay, a few standout tracks but mostly okay and was done by SMT veteran Tsukasa Masuko.

The real highlight are the dungeon/boss themes. The dungeon songs are actually played in canon which is cool because like I said earlier they're used to keep the residents of Mobius dependant on it. Each dungeon has a unique song as well as an instrumental version that plays when you aren't in battle and a remix that plays when you fight the boss of the dungeon.

These songs were composed by famous Japanese guest artists and their efforts combined with the excellent performances by μ's VA create one of the best collection of character songs in video games ever. Her performance is so good, it's hard to tell that it's the same person singing all these songs sometimes.

Some highlights I'd recommend listening to regardless of whether you play the game or not are CosmoxQueen, Distorted Happiness, Cradle, Suicide Prototype and Orbit. Writing this made me go to Spotify and start listening to the music again (you should too)

Gameplay
It's a turn based jrpg but with some cool twists. You can have up to 4 members in a party and each character can have 3 actions per turn. Combat is based around a system called the Imaginary Chain that shows you how the actions you choose will play out as well as what the enemy will do alongside a percentage that shows how likely your attacks are to be successful. You're supposed to adjust the timing of your attacks to maximize your damage, dodge enemy attacks as well as support your teammates by following up on what they do.

There are a lot of cool systems but the game is too easy for you to need to use all of them. Playing on hard does help give some of the bosses actual challenge but it also makes dungeon encounters more tedious than they need to be. What I did was swap between easy and hard when I was exploring a dungeon and when I'm doing a boss respectively.

Dungeons are meh, just a bunch of corridors with some occasional nice puzzles. Music and combat are great though so it shouldn't be a big issue.

Changes made in Overdose
Overdose added social links for the villains too and honestly I'd rank some of them over the GHC ones.

It also added the ability to play alongside the villains. It's not a typical route split though, early on in the game the main villain finds you and asks you to join her side since you're the powerhouse of your team as well as the leader. She knows better than to force or blackmail you though so instead if you agree to hear her out she lets you operate with the Musicians under a codename and a costume that doesn't reveal your identity, that way you can help both sides until you decide who you really support. Getting the good or bad ending is based on a decision you make before the final boss so there's no need to worry about accidentally locking yourself to a route.

In theory all this is great and l do like the new segments with the villains alongside new social links that they get, but the execution is sorta lacking. Every few dungeons the story stops for the villain segments which are just redoing past dungeons but with the villains. But besides that the ability to play with the Musicians along with their new social links ensures that every character in the game is fleshed out pretty well.

Overdose Changes part 2
Besides that Overdose also massively revamped the UI for gameplay and regular dialog. The gameplay UI is far superior to the original and the new camera angles are really good at letting you see the action. The general aesthetic is worse than the vita version though. It works perfectly but it lacks a bit of character.

Overdose also has different lighting since it's basically the original game moved into Unreal Engine 4 and the new lighting is worse. Not a terrible issue, but some areas can be really bright and the new lighting is actually worse at showing of details on character models compared to the Vita lighting which was cooler in color tone and fit the pale art style more.

Overdose also added new characters for both the GHC as well as the Musicians and they're integrated very well. I didn't even know they weren't in the original game until a friend told me. They come with new social links to do as well as a mini story that connects them and it's very well done. I was honestly more invested in this side story than I was in the main story, which I don't mind since this is a character based game. Sadly for some reason this side story doesn't get a satisfying conclusion at all. If you get the best ending possible it just sorta ends with minimal conclusion and this bummed me out.

Conclusion
Good story, great characters and music alongside great gameplay make this a must play for anyone who can tolerate slightly janky low budget games. Every now and then I get a sudden urge to return to this game, it's world, music and characters. It's just that good. Even if you didn't like the game you have to admit that it's proof of potential for something really good, I've been playing the sequel recently and I think it's lived up to that potential, I have to beat it first to know for sure lol.