Illusory Urahara, located in the vicinity of a shrine in Harajuku, is the only purely optional Idolasphere in the game. Rather than a dungeon, it is an arena where the player can earn rewards by taking part in series of battles. Arena battles come in four difficulties: Beginner, Intermediate, Advanced, and the Legendary, the last of which only being available when playing on a New Game+ save. One round in the arena consists of five battles against Mirages without a break. If the player wins, the option is given to continue with encore performances against a second and third wave of enemies; each encore triples the arena coins rewarded. The arena also offers a daily challenge battle; a special fight that can be challenged once per day.
Additional rules of the arena include:
- The player cannot swap active party members out during arena battles.
- The player cannot use any items during arena battles.
- Losing in the arena is the same as losing in a standard battle and will result in a Game Over.
- The player can attempt to run from battle at any time at the cost of forfeiting any arena coins they would have earned.
In addition to the battles held at the arena, as the player progresses through the game they have the opportunity to 'scout' several Mirage NPCs from within the other Idoloaspheres as part of a sidequest issued by the Mirage who runs the arena. Scouted mirages will appear within Illusory Urahara and the player will be given the chance to trade their consumable items and Performa for other Performa in a sequence similar to the Demon Negotiation mechanic from ATLUS' flagship RPG series, Shin Megami Tensei.
Aside from being a location where the player can test their skills and grind weapon mastery and EXP, the Urahara Arena is notable for being the only source of Perfoma needed to create each character's strongest Carnage, the only infinite source of Master Seals and Incense (obtained through trading Detritus with Nieg, a scouted Mirage), as well as a few accessories that cannot be acquired anywhere else.