You can access New Game + by exchanging one Badge of Honor at one of the vending machines in the Developer's Room. This feature allows you to start a new game while carrying over any EXP, FP, skills learned, money, and items (besides the Charm of Karachi, Chocolate Bar, and Radio).
Your party member's levels will be the same as the previous playthrough, but if unless you get the same Stand from the Personality Evaluation, yours will not. This is due to each of the 18 Stand users being counted as separate characters in the database. However, the current Stand user's level will be retained should you select them on a future playthrough. For example, if you start out with Howlin' Wolf, then start a New Game + and get Miracles, your level will reset to 1. However, if you clear the game with Miracles and get Howlin' Wolf again, you'll have the same stats and skills as when you ended your first playthrough. However, using Cinderella to change back will reset your level to 1 regardless.
The game only counts the amount of repeat playthroughs on that save. This means that bad endings, Josuke's endings, and secret endings like the Dio and Hol Horse End will not be counted, as you cannot start a New Game + from them. Therefore, it's important to keep a save where the Developer's Room can still be accessed if you're trying to reach said endings and don't want to lose your progress.
If you're not sure how many times you've cleared the game, you can talk to Holly in the Developer's Room and she will tell you.
A few of the major differences on repeat playthroughs are as follows:
- Cleared the game once (2nd playthrough & up)
- Easy Mode is now disabled when starting the game.
- You can enter your parents' and sister's room in your house.
- Diavolo now appears in a hidden location on nearly every map. He can be battled and defeated for money and EXP.
- You can now use the computer in Emporio's Room to play the Stand Summoning Program minigame.
- A shortcut to Sundarbans will appear in the SPW Foundation Camp.
- Cleared the game twice (3rd playthrough & up)
- You can now start a New Game + for free, without trading a Badge of Honor.
- Cleared the game three times (4th playthrough & up)
- Utah can now be battled in Edfu.
- The Unrest and Succession endings are unlocked.
- If you fail the final battle with Vins and are sent to the Sanctuary, a door leading to the Dream World appears.
- Cleared the game six times (7th playthrough & up)
- The pig toilet in the debug room now has a door behind it. This door leads to a secret room where you can see all the original Stand sprites.
- Cleared the game ten times (11th playthrough & up)
- Vins now appears in the Debug Room. Talking to her after attaining the Succession End will let you go to the Dream World.
- Talking to Anasui in the debug room will now let you change sex.
- You can fight Clayman's true form in the Debug Room.
- New items are available from the vending machines in the Developer's Room.
- Cleared the game 30 times (31st playthrough & up)
- You can now save using the radio in the Developer's Room free of charge.