The story is a continuation of the events depicted in Persona 4 Arena and begins the day after the previous game concludes, meaning Arena Ultimax is also set in May 2012.
The Midnight Channel is back on the air and once again broadcasts a strange advertisement for another fighting tournament christened P-1 Climax, also known as Operation: World Destruction, that shows members of the Investigation Team and the Shadow Operatives in combat. Just moments after this, Inaba is subject to a power outage and is engulfed by a bizarre red fog. Furthermore, figures that look suspiciously like Mitsuru Kirijo, Aigis and Akihiko Sanada being crucified are shown on TV. While the Investigation Team attempts to figure out what's going on, Junpei Iori and Rise Kujikawa becomes trapped in the red fog, while Labrys, Ken Amada, Koromaru and Yukari Takeba ride on a helicopter to see the fog engulf Inaba.
The storyline is split between episodes. Episode P4 is the starting point to the plot that takes place immediately after the Arena storyline, and follows the viewpoints of Yu Narukami and his return to Inaba for the Golden Week. It also follows Naoto Shirogane in her investigations on the Kirijo Group Ergonomics Laboratory, Rise Kujikawa's visit to Inaba and her resolve to return to show business, and each of the Investigation Team's experience when the red fog settles into town. These culminate into their meeting with the Shadow Operatives and subsequent climb of the mystery tower on the site of Yasogami High School.
Episode P3 is unlocked after the player completes Episode P4 at 94% and follows Labrys and the Shadow Operatives investigation on Shadow activity in Inaba, before being ambushed and captured by the Malevolent Entity and his accomplice. It also follows the viewpoints of Yukari Takeba and her acting career, Ken Amada's attempt at normal student life with Koromaru, and Junpei Iori's coaching for a junior baseball team. These lead to the meeting with each of Inaba's Investigation Team, and the rescue of the captured Shadow Operatives members at the mystery tower.
In both of the Episodes, the player battles the fake "Shadow" versions of every cast, being released by General Teddie who used the red fog to bizarrely transform Inaba and disable all electronics and communications. They will then face Sho Minazuki, General Teddie's accomplice, who is carving Persona fragments from the fights with the fake Shadows. The Persona Fragments was to be used along with all the Shadows that exist in Inaba to summon the Entity's true form, Hi-no-Kagutsuchi.
Episode Adachi is the DLC third episode that follows Tohru Adachi's life in incarceration awaiting his trial, and Sho's recruitment for him to follow through with the plan to collect the Persona fragments. However, Sho's other personality Minazuki reveals that the real plan was to create a world where only Sho will exist in solitude, and to this they plan to summon, weaken and enslave the Entity's true form. Sho plans to have Adachi's power from the Sagiri merged with the Persona fragments, but Adachi betrays Sho in the final moments, just as Yu arrive to stop the villains.
In the end, the Entity also betrayed Sho by taking over his body as vessel for his true form. The character facing Kagutsuchi for the final battle also depends on the Episodes: Labrys in Episode P3, Yu in Episode P4 and Adachi in Episode Adachi. Kagutsuchi appears in its fiery form above Inaba and it takes several hits by the protagonists to defeat it. There are multiple endings to the story, depending on the choices made during the final chapter on Episodes P3 and P4. The normal ending follows the Investigation Team saying goodbye to the protagonist at the end of Golden Week, the Shadow Operatives decision to follow through with their own separate and normal lives and Sho Minazuki escaping with his whereabouts unknown. The true ending reveals that Sho has lost his other personality but is able to summon his own Persona, and he decides on to go on his own journey, insisting that he will kill Yu and he should be ready for him at anytime. Yu, Labrys, the Investigation Team and the Shadow Operatives will be meeting at Junes Department Store at the end of Golden Week to know more about each other and strengthen their bonds.
The gameplay in Persona 4 Arena Ultimax is still that of a. However, substantial changes to characters and the system have been made from Persona 4 Arena. A 1.10 Patch was eventually released as well for both arcade and console versions. More custom announcers for both arcade and console versions have also been added.
The Episodes in Story Mode has a completion percentage which stops at 94% on Episode P4 to unlock Episode P3. Each Episode has a two-choice question in the final chapter before the fight with the final boss where both should be selected to unlock the True Ending at Episode P4 and achieve 100% completion for both episodes. Players do not need to replay all chapters in both episodes to get full completion, only select the final chapter and win the final battle.
The console version compared to the original P4U, has received many more changes. Such as new console exclusive characters, and all the themes being rearranged to their OST disc versions; by proxy, the original characters' themes from the first game are also the OST disc versions as well. There are also several new modes of play as well that were not available in the original Arena game, as well as extra tweaks to the AI in said modes.
Changes from Persona 4 Arena
- The original Short-Hop mechanic can now be cancelled into from an attack with less startup, but said types of attacks can now be blocked both high and/or low.
- Evasive Actions can now be Guard-Cancel-Rolled into at the cost of 50 SP.
- Recovering from certain attacks or getting counter hit normally will cause a counter hit state as usual, only some moves now provide a window of a free Fatal Counter hit, which makes the aforementioned moves more risky than before, as well as providing new Fatal Counter combo opportunities. This new state is known as "Fatal Counter Recovery".
- A new system implemented is known as the "S Hold System" (also known as the "Skill Hold System") which is a special attack which changes its properties the longer the A/weak attack button is held down, physically shown as a meter on the screen (Skill Boost, SP Skill, Awakening SP Skill then Instant Kill in that order of held-down duration).
- Enhanced Super Moves called Skill Boost SP Attacks allows characters to perform a much powerful SP Skill Attack by spending 75 SP instead of the usual 50 SP and using two associated buttons instead of one (much like how one does a normal Skill Boost).
- All characters' Barrage/Auto-Combos' first inputs (5A) are unchanged from the previous game, and a few characters, namely Yu and Akihiko, retain the same second inputs (5AA) as well. All other characters' auto-combos differ past the first hit for the normal version of their character, while Shadow versions of characters retain the old auto-combo from the previous game.
- Shadow Labrys (Asterius) is the only returning character from Persona 4 Arena whose auto-combo has not changed in Ultimax.
- Elizabeth is the only character who can also access the first 3 inputs of her original auto-combo via repeatedly pressing the strong attack input (5BBB), thereby making her the only character with two auto-combos.
- Super Cancels now convert 6.5% of one's HP into blue heath instead of just 5%.
- Ultimax enables the traditional extra Super Meter bonus on first attack landed after the round's start, where an additional 10 SP bonus is given (even for both characters if they managed to both counter hit themselves and land the first attack at the same time).
- The overall damage of characters has been toned down.
- A new blue HUD based on Persona 3 replaces the previous yellow Persona 4 HUD.
- Exclamation marks not only appear above the characters' heads as usual in recent games for any incorrectly blocked moves, but also during a Negative Warning.
- All characters now have different Persona Cards/Units from each other, while in the previous game, they originally all had 4. Shorter unit characters are more susceptible to Persona Break, but can recover from it much sooner. Longer unit characters take longer to inflict with Persona Break, but recover from said state much later. The following returning characters now have these numbers of Persona Cards/Units each:
- Yu: 4 Cards/Units
- Yosuke: 3 Cards/Units
- Chie: 3 Cards/Units
- Yukiko: 5 Cards/Units
- Kanji: 3 Cards/Units
- Teddie: 5 Cards/Units
- Naoto: 4 Cards/Units
- Akihiko: 2 Cards/Units
- Mitsuru: 4 Cards/Units
- Aigis: 4 Cards/Units
- Labrys: 3 Cards/Units
- Shadow Labrys (Asterius): 6 Cards/Units
- Elizabeth: 6 Cards/Units
- The All-Out Rush D finisher now needs 18 hits total in order for the final hit to Fatal Counter.
With the exception of Elizabeth, Margaret, Shadow Labrys with Asterius, two versions of Sho Minazuki, Tohru Adachi, and Marie, there exists an alternate version of characters based on the Shadows of the Persona series. Shadow-Type characters are more geared towards the offense as they build more SP as they attack and their SP is carried over between rounds. Shadow-type characters utilize the character's original auto/dial combo from Persona 4 Arena and can use Awakening SP Skills with 100 SP. Shadow-Types are also altered on their stats in comparison to their normal counterparts, as they all have 2000 plus HP and deal 20% less damage overall.
In addition, they gain access to a mode known as Shadow Fury/Frenzy (Shadou Bousou, lit. Shadow Rampage), which gives them unlimited SP for a limited amount of time and is activated by what would be the Burst command while the character is at 100 SP. In compensation for these additions, they lose major defensive techniques, mainly Bursts and Awakenings despite their larger HP amount. Thus, this makes the Shadow Type a high-risk, high-reward playstyle with an emphasis on skill usage.
In the case of Labrys and her Shadow mode(s), there is both a Shadow Mode Labrys (with Ariadne) and the original Shadow Labrys (with Asterius).
Patch 1.10 Changes
The 1.10 Patch changes a few more things compared to the previous game's patches. However, unlike the P4U patches, there is no visual indicator for patch versions.
Also, like the previous game's patches, this patch is already in place by default for the console versions.
- Guard Cancel Evasion now has less total frames of animation, and travels a further distance. Also no longer causes a Fatal Counter Recovery state (and causes a normal counter hit state instead).
- Shadow-types have been changed up:
- Shadow-types now have a 2000 HP increase from their normal versions.
- Awakening SP Skills can now be used with 50 SP as the cost.
- One More! Cancels and Guard Cancels have their SP cost halved during Shadow Frenzy
- Activating Shadow Frenzy standalone no longer causes a freeze frame, meaning the opponent can move around during that time. However, it still possess complete invincibility throughout its animation.
- For the Suplex Hold System, the gauge appears faster when the button is held down, and the MAX level stays on screen for much longer before disappearing.
- The All-Out Rush C button finisher is now always a Fatal Counter on the final hit, regardless of zero-or-how many extra hits via button taps have been added.
- All characters have received character-specific changes here: 
- Yu Narukami
- Yosuke Hanamura
- Chie Satonaka
- Yukiko Amagi
- Kanji Tatsumi
- Naoto Shirogane
- Akihiko Sanada
- Mitsuru Kirijo
- Shadow Labrys
- Yukari Takeba: The Unsightly Pink Sniper (ドぎついピンクスナイパー Dogitsui Pinku Sunaipā, a reference to the fact that she's wearing her Pink Argus costume.)
- Persona Cards/Units: 4
- Junpei Iori: The Mighty Strike-Out Slugger (逆襲の全力空転スラッガー Gyakushū no Zenryoku Kūten Suraggā, a reference to his baseball theme and his constant failings.)
- Persona Cards/Units: 4
- Sho Minazuki
- Solo/Sho: The Rule-Smashing Pun Machine (掟破りの駄洒落マシーン Okite-yaburi no Dajare Mashīn)
- No Persona Cards/Units
- Persona/Minazuki: The Scar-Faced Dark Messiah (創面貌（スカーフェイス）の黒き救世主（メサイア） Sukāfeisu no Kuroki Mesaia)
- Persona Cards/Units: 4
- Solo/Sho: The Rule-Smashing Pun Machine (掟破りの駄洒落マシーン Okite-yaburi no Dajare Mashīn)
Console Exclusive Characters
- Rise Kujikawa: The Scandalous Superstar Idol (完全変態☆スーパーアイドル Kanzen Hentai Sūpā Aidoru. "Kanzen Hentai" is a for "totally perverted", a reference to her Shadow; and " ", a reference to the fact that Himiko has undergone a drastic change from a navigational Persona to being capable in fighting.)
- Persona Cards/Units: 4
- Ken Amada and Koromaru as one playable character: The Pretentious Tenderfoot Duo (生意気盛りの皮肉屋新人（シニカルーキー） Namaiki-sakari no Shinikarūkī, a reference to Ken's seriousness and naïveté and the fact that he and Koromaru play as a single character.)
- Persona Cards/Units: 2
- Tohru Adachi: The Egocentric Police Dick (完全自己中キャベツ刑事（デカ） Kanzen Jikochū Kyabetsu Deka, a reference to his egotism and the fact that he is a former police detective. "Dick" is a play on both his personality and his former profession, while the Japanese title includes "cabbage", a food that he is said to eat often.) (DLC Character)
- Persona Cards/Units: 4
- Marie: The Antisocial Poet of the Hollow Forest (虚ろの森のツンデレ詩人（ポエマー） Utsuro no Mori no Tsundere Poemā, a reference to her dungeon, her personality, and her habit of expressing her thought into a poem.) (DLC Character)
- Persona Cards/Units: 5
- Margaret: The Sadistic Stud-Keeping Secretary (イケメン飼いのドS秘書 Ikemen-gai no Do Esu Hisho), a reference to her position as an assistant in the Velvet Room, all the Personas she uses in-game are male, and how she kissed Yu the day before he leaves in the True Ending. (DLC Character)
- Persona Cards/Units: 8 (Note: Margaret actually recovers her Units akin to 4 Card/Unit characters)
Persona 4: Arena Ultimax 2
As of January 15, 2015, an updated version of the original Ultimax game, known as Persona 4: Arena Ultimax 2 (Persona 4: The Ultimax Ultra Suplex Hold 2.0 in the Japanese version) was announced. This version as its name states, is an updated version of the game that provides all sorts of balance changes compared to the original. This version also takes all of the console-exclusive characters and adds them to arcades.
It is currently unknown if a console version of this version will ever be released in the near-future.
Changes from Persona 4: Arena Ultimax
- All console-exclusive characters added to the arcade versions.
- Shadow-types now have re-tweaked mechanics.
- Shadow-types can now use Defensive Bursts.
- All Shadow-types have a 1000 HP increase from their normal counterparts instead of a 2000 HP increase.
- Shadow Kanji and Shadow Akihiko only have a 500 HP increase.
- Attack power increased by 10% from the original Ultimax game.
- SP gain rate adjusted, and no longer carries between rounds.
- Shadow Frenzy now uses the Burst Gauge to activate instead, and now uses the current amount of SP as a timer to judge how long it lasts.
- Opponents cannot use Defensive Bursts during an active Shadow Frenzy.
- If activated at 100 SP, the Shadow-type's Persona Gauge is filled up to full.
- SP usage during Shadow Frenzy is adjusted. SB Skills use 10%, SP Skill Attacks use 20%, SB SP Skill Attacks use 30% and One More Cancels use 25%.
- Suplex Hold System is only usable in single player.
- Skills performed through this mechanic no longer possess the Auto/Barrage Combo attribute.
- Location of SHS gauge changed.
- Taking damage will no longer interrupt the charging period, and the gauge has increased charge speed.
- Decreased lag time between button release and the execution of the SHS-based move/skill.
- Decreased time for holding down button between gauge disappearing.
- The Barrage/Auto-Combo's SP and Burst Gauge bonus is instead given on the 4th input (the Skill portion) as opposed to the 3rd input.
- All-Out Attacks can now be teched on air-hit.
- Has increased pushback on block, but will not apply when blocked in the corner.
- All-Out Rushes can be done while holding down A or B instead.
- Normal Ground Throws can now be special-cancelled into Skills on hit, and are adjusted to deal around the same damage.
- Freeze can be now be escaped through button mashing also.
- Status Ailments or any bad statuses overall are now shown on the HUD when they occur.
- Panic/Confusion state adjusted. Holding in any direction now causes blocking instead of inverted controls.
- Forced guard state after stagger has been removed.
- Persona Break indicator location has been changed, and will shift more towards the HUD of the character who was inflicted with it.
- Damage has overall been adjusted and SP Skills now deal even less damage, with even less minimum damage.
- Proration amount for damage scaling has been adjusted for several moves.
- A number of multi-hitting moves now only apply proration once.
- Personas when they appear, now have a brief amount of invincibility just before their attacking animations' active frames.
- When two Personas collide their attacks, they now normally clash.
- Knockdowns caused by Defensive Bursts can no longer be countered by another Defensive Burst.
- One More! Bursts no longer push the user away when used on their cornered opponent.
- SB Skills are adjusted in that they only drain/use up SP only at the very moment they come out.
- Various items and objects now have unique colors each to easily differentiate between owners, such as Teddie's various attacks.
- All characters once again, have had character-specific rebalances here: 
Shadow Version Boxart
Seen at the very end is a glimpse of "Shadow Yu"
Artwork of Aigis defeating Yu
Japan Special Edition
P3 Mode Epilogue
P4 Mode Epilogue
- Like its predecessor, the game's official Japanese website once again featured Aigis and Yu Narukami fighting in a duel. However, Aigis is seen defeating Yu with a massive suplex, which befits the Japanese title of the game.
- If you compare the normal box art and the shadow box-art, Adachi's facial expression changes from smiling (standard) to worried (shadow).
- Persona 4 Arena Ultimax is the last game to feature Laura Bailey voiced as Rise due the her busy schedule during development of Persona 4: Dancing All Night.
- The Shadow Types do not share themes with their other selves, as all of them have their own distinct themes, all of which have been taken from either Persona 3 or Persona 4:
- Shadow Yu: Reach Out To The Truth - First Battle
- Shadow Yosuke: ZONE TIME
- Shadow Chie: Backside of the TV
- Shadow Yukiko: Castle
- Shadow Kanji: Sauna
- Shadow Teddie: Borderline of Madness
- Shadow Naoto: Secret Base
- Shadow Rise: Striptease
- Shadow Yukari: Calamity
- Shadow Junpei: Deep Breath Deep Breath
- Shadow Mitsuru: Shadow
- Shadow Akihiko: Crisis
- Shadow Aigis: Master of Shadow
- Shadow Ken & Koromaru: That Which Comes from the Darkness
- Shadow Labrys (Ariadne): The Almighty
- Newcomers possess moves their Personas normally do not learn:
- Rise's Himiko can perform both Tetrakarn and Makarakarn, as well as even Arrow Rain.
- Ken can perform Thunder Reign, which neither Nemesis or Kala-Nemi can learn naturally.
- Adachi with Magatsu-Izanagi can use Megidola, though it can only use/comes equipped with Megidolaon in Persona 4 Golden.
- There have been files found in the game's data that suggests that a Shadow version of Marie was planned.
- There have been files found in the game's data that suggest the German Demon Mephistopheles was going to appear in the game.
- In the second episode of the 2017 anime series , the characters Keita Amano and Tasuku Uehara play the arcade version of Ultimax. Tasuku's Teddie defeat's Keita's Yu, without losing any HP. Two other characters are shown in a fight between Chie and Akihiko.
- Official Atlus Japanese Website
- Official Arc System Works Japanese Website
- Official North American Website