Akira Kurusu was standing outside a building looking at his phone. His GPS had led him to the mansion of Totoya Bando, a prominent attorney in Japan. He had gotten wind of some rumors he had heard at the crossroads bar about how he would falsify evidence to get people arrested, therefore winning cases. After doing some digging, he found the location of his house.

He opened up the mementos app and said his name. A match showed that he had a palace and that his mansion was where it was located. Akira thought about what an attorney would have as a palace.

He tries the most obvious answer: "A courthouse". It works. Now that he has the full location, it was time to head back to his gang. However, before he could, he hears sirens in the distance. Not much later, several police cars show up to the front of the mansion.

Then, a crash sounded from above him. It was a window breaking from a man jumping through it. The man was falling near Akira so he ran out of the way to avoid being seen. Hiding behind a building near the mansion, Akira got a good look at the thief. He was relatively young looking with a red coat and huge smile.

The man runs down an alleyway while beckoning someone to follow him. Just then, two more men jumped out of the window and followed the thief into the alleyway. Akira, feeling a strong sense of justice, follows after them. He figured by learning about them, he could have new hearts to steal. The more criminals changed, the better right?

He lags behind so as to not be seen by them and eventually, they stop. Akira hides around a wall. He overhears their conversation.

"Man, that was friggin' close." said the man that looked like a gangster.

"This will be tougher than I thought, but it's nothing we can't handle." Says the thief in the red jacket.

"I sure hope so, the lock only opens with Bando's DNA. Just using a disguise won't cut it."

"Relax Jigen, I already have a plan in mind. Let's get back to the hideout for now though. It's too dangerous with the cops around."

"Alright, this better be a good plan Lupin."

A gasp arose for Akira. What did he just call him? Hearing Lupin's name, he felt a surge of energy bursting through him. It was a similar feeling to when he got his persona for the first time. Unfortunately, the thieves seem to have heard him.

"Someone's there!" Jigen yells before shooting a few bullets in Akira's direction. Akira runs as fast as he can from the thieves.

"After him!" Someone shouts. Akira now regrets the fact that he went alone for this mission (Even Morgana wasn't here. He stayed at the café due to being sick). So with no other option, he activates the mementos app and travels to Bando's palace. He'd figure he'd lose him by going there. A familiar black and red portal forms around him as he's taken to the other dimension.

Once there, he looks at the palace in front of him. It was a large courthouse painted in brown and gold with a clock at the top of the building. It looked to be about six stories high. There was a courtyard with a fountain of Bando depicted as a judge.

Feeling safe, Joker lets out a sigh. He turns to walk to the courtyard when something grabs his jacket.

"Finally caught ya, you little bastard!" It was Lupin! He followed him into mementos. "Now what were you-" Lupin turns Joker around only to stare at him. Lupin had caught a child. Knowing this now, he lets go of Joker.

"Sorry, didn't mean to be so rough. But I want to know why you were following us? Also, what's with the get up?" Lupin briefly looks away for a moment and does a double take. He was no longer in Japan. The startled thief yelps before turning back to Joker.

"Where in the hell are we?" Before Joker can answer, a siren is heard. Then, a spotlight shines on both of them.

"Intruders! There are intruders here!" Someone shouts. Joker gets into a battle stance as a bunch of shadows surround the two. Lupin's face grows even more confused.

"Just my lucky day." He sighs as he pulls out his walther. Not having his normal insight to the shadows, Joker could only guess as he brings out his persona Horus. Lupin stares in shock and amazement before focusing back on his enemies.

Lupin starts shooting the shadows while Joker knocks down two enemies with Megido. Both were holding strong in the fight, with each of them noticing the other's skill. Lupin thought the kid was amazing and wanted to know more about his power. Joker was impressed, finally seeing what the real Arsene Lupin was capable of.

While Lupin had scored three more kills, he didn't notice a bigger shadow coming from behind. Using a taser, it shocks Lupin in the back. The thief drops to the ground, conscious but hurt. The bigger shadow grabs his neck in a chokehold and shouts to Joker who was still fighting.

"Thief, cease your fighting right now or your friend dies!" Joker stops. He looked at Lupin. The thief was struggling to breathe, grabbing at the arm around his neck. Joker felt a strange desire to help. He knew he was a criminal, but if he really was Arsene Lupin, then he'd be like the gentleman thief he'd read about, only taking from those worse than him.

Joker recalls his persona and holsters his weapons. The bigger shadow laughed as he let go of Lupin. Both thieves were chained and taken to a prison cell.

"Wait here until the judge is ready to hold a trial." The guard said before he left. Alone at last, Lupin decides to break the silence.

"I could've handled that thing back there, but thanks anyway" Joker nodded in response.

"I suppose now's a good time to introduce ourselves. I'm Arsene Lupin the third, thief extraordinaire."

"The third?" Joker asks in surprise.

"I'm Arsene Lupin's grandson."

"I see." With Lupin knowing about Mementos, he had to tell him about his secret. "I'm Akira Kurusru, high school student and phantom thief, like you. My code name is Joker."

"Starting young like me, huh? Looks like we got a lot in common."

"Not exactly."

"Hm? What do you mean by that?" And also, what is this place anyway?"

"I'll answer all your questions, since we're stuck here anyway. This is Mementos, a world insides the hearts of men. Each person has desires, but when they grow distorted, palaces form. We're in one right now."

"Doesn't look like a palace to me."

"The palace reflects what the person sees a particular place as. Like how an artist sees his home as a museum."

"Oh, because this man's a lawyer, he views his mansion as a courthouse! I'm getting it."

"What I do in this world is I steal the desires of corrupt men. By doing so, their desire for evil is gone but the weight of what they do remains."

"So they end up confessing their crimes in the real world?"

"Yes."

Lupin smiles. "That's brilliant, putting bad guys behind bars by making them good. Wish I could do that."

"Really?" Joker asks, surprised.

"Yeah, I hate the kinds of criminals who kill and steal from good people trying to live honest lives. It's why I only steal from those who can take the loss."

Joker stares before smiling. This really was the gentleman thief he read about.

"What about the weird bird thing?" Lupin asks.

"That's my persona, Horus. A persona is another part of me. One that I can control to fight. Each one does something different like fire attacks or-"

"Each one? You have more?"

"Yes. Actually, there's one I want to show you. He's my first." Joker takes his mask off to summon Arsene. He appears in blue flames.

"This is my persona, Arsene Lupin." Joker says. Lupin stares in amazement.

"You named him after my grandfather? I can see the resemblance a bit. It's flattering really. Seeing as it's a part of you, this makes you a true thief like me."

"Now I have a question." Joker says, putting his mask back on. "What were you doing at Bando's mansion?"

"I came to steal his watch collection. He uses his dirty money to buy watches worth over millions of yen. The bastard might learn some humility once he's lost his precious time pieces."

"He'll definitely learn when I steal his desires, or heart." Joker says.

"Looks like we both want to steal something from him." Lupin says, stepping closer. "How about you and I team up for this heist, both here and in the real world?" Lupin extends his hand.

"Yes, I consider it an honor to work with the gentleman thief himself." Joker takes his hand and they shake.