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SMT × Persona Crossover
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Published:
2025-08-31
Updated:
2026-05-04
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54,034
Chapters:
19/?
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Agent of Satan, Slave of Law

Summary:

He observes as Saika Takao roams inside the Metaverse as a Phantom Thief. Though lacking the power of Persona, she was gifted with the power of Demon Summoning. And without the rebellious will, her heart is vulnerable to corruption. In this eternal conflict of Law and Chaos, they’ll emerge victorious. Under his guidance, his pawn Saika will have no choice but to make a sacrifice, bathe in the blood of her friends. And eventually, recreate the world through the Conception.
A world without sin, just like what he intended.


(A P5R and SMT fusion with an OC protagonist. Could be read without the context of one fandom.)


This fanfic had been fully outlined.
Current status: important update.

Notes:

(See the end of the work for notes.)

Chapter 1: Wheel of Fortune

Summary:

Content warning for the chapter: description of torture.
Be aware that this fic would trigger heavily religious people (mostly Abrahamic religions). This includes:

  • Usage of several occult, Pseudepigrapha, and/or Apocrypha texts.
  • Morally ambiguous and cynical depictions of several religious/mythological figures.
  • It's Shin Megami Tensei, they're going to kill God at one point or another.

-
I don't cross-post on the other fanfiction sites.
Spam accounts will be reported. ConCrits are welcome.
Hope you would enjoy my Megaten brainrot.


- Revisited and edited on 2025/9/21.
- Revisited and edited on 2026/3/9.

Notes:

Table of Contents
[Castle of Lust]: 1-13 (~33,000 words)
[Museum of Vanity]: 14-18 (unfinished)
Update: 19 (will be replaced by a rushed-finale eventually)

 

(See the end of the chapter for more notes.)

Chapter Text

...He brought me a small ring with an engraved stone seal on it, telling me, "Take, O Solomon, king, son of David, this gift from the Lord God, the Most High Lord of Hosts. With this ring, you shall bind all the demons of the earth, both male and female; with their help, you will rebuild Jerusalem." 

—Testament of Solomon, verse 5. 




















[2016/4/11 Monday, Early Morning]

The train was delayed. Saika Takao ended up going to school with Ryuji Sakamoto and another Shujin student. 

Raindrops kept making pitter-patter sounds. A reminder that she forgot to bring her umbrella today. 

Fortunately, short hair was easy to dry. 

“Damn it… screw that pervy teacher.” Sakamoto ran close to them as that bastard drove his car away from them. 

Saika would’ve liked to stop Takamaki from getting into the car, but it was already too late by the time she’s out of the subway station. 

Under the roof, there’re three students—herself, Sakamoto, and a boy with glasses. 

Sakamoto was no more than an accomplice, allied together in the shared hatred of Kamoshida. Had told him to dye his hair back to black a couple times last year. It didn’t work, Saika could only give up. 

Strangely enough, the glasses boy made no reaction when Sakamoto insulted Kamoshida. He wore a Shujin uniform with a second-year pin. But no matter how much Saika chased her memories around, she could not recall the same face somewhere else. 

“You are wearing that black blazer, so you are also attending Shujin Academy, right?”

The boy with glasses looked at them, dumbed. Saika paused, how did she not realize this earlier? This is the transfer student Ms. Kawakami talked about. Saika gave a quick scan on the boy’s attire—black sheepy bed hair, glasses, fair skin, and he wore the uniform as it’s intended. Look at you, Sakamoto. 

“You’re the transfer student, correct? No wonder why you didn’t recognize Kamoshida.” 

Saika scanned the boy’s overall attire. He had a sheepy bed, black hair, and wore glasses. “Speaking of which, I’ve never met you… Oh, you are that transfer student, no wonder you know nothing about Kamoshida.” 

However, it doesn’t stop Sakamoto from his rants about Kamoshida. Or more accurately, because there’s a transfer student who knew nothing about Kamoshida, so he has to say more of them. “He is that kind of guy who does whatever he wants. He might have convinced himself that he was the king of a castle.”

“Remind you, we will be late soon if you keep up with your ranting like this.” 

“Oh, right.”

With Sakamoto in the lead, they walked through the alley. They walked to the front of a giant medieval castle. It was made of brown bricks with purple sky looming over it. 

“...Did we take a wrong turn?”

“No way, it’s the same path I took to school every day.” 

Why did a castle have the words Shujin Academy carved on the wall anyway? Must’ve been a hallucination. They started to retrace their path. 

It’s the same castle. A castle too real to be in a dream. Maybe its environment made for a movie? Who knows? Without any other choices, they walked into this place. 

The main hall was fancy. A huge crystal chandelier hung on the roof, red carpet spread on the checkerboard floor, elegant wall lamps illuminate the scenery. On the far wall hangs a painting in which the figure has the face of Kamoshida. 

A strange floating creature approached them. It got a green witch cap and cloak, the head was a Halloween pumpkin. White-gloved hand carried an oil lantern. 

Saika put her arm over to stop the transfer student from petting it. 

“Hee-ho! Who are you guys, ho? Are you guys here for the Magatsuhi fe-hee-east too, ho?”

It didn’t take long for more pumpkins to approach them. They were surrounded, examined by those weird creatures. 

“Wait, you guys ain’t demons, that means…” Demons?

“Intruders, ho!” 

Those demons approached them. It all happened too fast. 

“We gotta run! Go!” Sakamoto broke out of the demons to create an exit. But then Saika heard the sound of a shaking lantern. 

“Agi!” A fireball came out of the lantern and badly burned Sakamoto’s leg. 

He led out a throat-ripping screech. “Damn it, the hell you think you’re-” 

“You can’t win!” Saika shouted. The differences in strength are too visible. One was a demon who knew magic, another was a high school student. One wrong move, Sakamoto could be burnt into nothing but ashes. 

“Take them away, ho!”

 

 

 

Halfway through, an armored angel approached the pumpkins. They had a conversation. They came up with a conclusion—she should be locked in a separate cell. 

“Anyone here?”

Anyone here?” Her own echoes answered. 

Empty wooden barrel, chains on the wall, and a dusty bed. There’s nothing useful. Her phone was out of service, too. Not even the camera worked. The only thing that worked was a weird app, she didn’t know when she had downloaded it. It has a weird eye icon too. 

Strange-shaped shadows loomed over the path outside. Three demons arrived here and started to talk. Yuko had a lot of books regarding mythology on the shelf, and Saika reads them when she’s free. Thanks to that, she’s able to recognize the figures outside. 

Agathion, inside his pot, floating in the air, said. “Seems like the king won’t come here to execute her now, what should we do?”

“Hey, listen, sonny. It is a good thing that King Kamoshida won’t check on that human gal for now. Unlike all the other people who suffer from torture daily, she ain’t a cognition, she is a real human being!” Said Incubus. 

Mandrake bent her back and put her hands on her face, frustrated. “So? Just say it, don’t waste our time.” 

“That means she could produce Magatsuhi! You dumb ass! Those demons favored by Kamoshida get to stay inside the Magatsuhi-rich areas while we are here to entertain him, and remain weak!” 

“Because she’s a real human, she had emotions, and therefore she could produce Magatsuhi. Gotta say thanks to that new Archangel guy who proposed to move her into a different place, I bet he planned to do this himself.” Incubus led out a maniacal laugh. “Y’know what we should do to provoke a strong emotion in her, don’t ya? We’ve already done it plenty of times in this castle.” 

“Torture her?” Said Agathion with his squishy voice. 

“Bingo.” 

“Then let’s hurry, we gotta do this before we get caught!” 

“Well, just be careful not to kill her. We don’t get to have Pixie on our side.” 

They were approaching, yet she remained powerless. The suffering begins. 

A tiny thunder pierces through her entire body, and then she could no longer move. Plenty of nails stabbed deeply into her body, she’s feeling asleep. But after she lost consciousness, she was slapped awake by Mandrake on the face. 

She hoped that she could feel numb to pain rather quickly, but it was only a pathetic hope. Whether it is fear, pain, or shock. Saika watched the demons giggling as they gathered the glowing red particles, or what they called Magatsuhi. 

Her skin was full of deep cut scars, bleeding, and her uniform was starting to stain. She screams in agony repeatedly in despair. 

She lost track of time. It could have been minutes or hours. 

Maybe she’s about to die, Saika closed her eyes, started thinking about the past to detach herself from the present, memories replaying inside her brain like an old film. 

She’s playing inside the orphanage just like any other kid. A group of bullies approached her and beat her up just to get the toys. 

“Scream as much as you like.” One of the bullies said. “The few adults are not there, and they couldn’t be bothered to save you.”

It happens a lot, and she often has to deal with her swollen scars as a result. There’s no one on earth she could rely on, not her parents, not the staff. 

To be honest, it’s such a bad way to cope with another pain. But if she has to bring up her happy memories, Saika would have to deal with the fact that important people from her life were gone forever. Her father, mother, and…

Suddenly, they stopped their torture altogether. “Hey, what are you doing here? You are an unfamiliar face.”

Enduring the pain, Saika turned her head to see the said unfamiliar face. It was a giant raven, no, an angel. 

He had grey skin, wearing a shawl and a robe. Golden halo shining on the back of his head, raven wings spreading out from his back. His long black hair was flowing out of his white shawl. He also wore a white square mask.

The angel replied to the demons with a word. 

“Megidolaon.” 

A giant white and blue light energy ball descends from above, devouring anything inside it as it expands. Within a blink, all three of them dissolved into Magatsuhi. 

She wanted to stand up, but immediately, she fell to the ground. 

“No need to force yourself up, the demons are gone, you are safe now.”

“Get out!” The captive yelled, crawling away from the angel. “I bet you are here for my Magatsuhi just like the other demons.” 

Saika herself was locked by an Archangel, after all. 

“Having a difficult time trusting people, aren’t you?” His voice remains calm. “It is understandable, after what they had done to you.” 

“Then explain yourself for everything. Who are you? Why are you here?” 

“I am the angel Mastema, a heavenly prosecutor from the kingdom of light.” He watches her calmly with sky-blue eyes and smiles politely.

 “It might be hard for you to trust my words, but I do not wish to harm you. I dwell in the realm of human unconsciousness in the hope of finding a way to cleanse those distortions that have affected my kind.” 

She wasn’t sure about the human unconsciousness thing. But that angel doesn’t seem to mean any harm. 

He could take advantage of the situation. But instead, he’s taking out those demons for her and answering the questions. Maybe Saika misjudged him. 

Saika softened her attitude, “I’m Saika Takao. Sorry for asking you another favor after all you’ve done for me, but there are two people I know who were also trapped in this place. Could you find them?” 

But instead, Mastema picked her up. 

“The most important thing right now is to find something to heal you up. You could fall into the hands of demons if I simply leave you there.”

 

 

 


 

 

 

Last Saturday was his first time in Tokyo. 

The city was crowded with people, unlike the countryside. He felt uncomfortable walking in the crossroads in Shibuya. Now, he’s living inside the attic of a cafe known as LeBlanc, located in Yongen-Jaya. 

He sent some IM messages to his mom with no reply. They see me as a criminal, just like any other. 

They got rid of a pain in the ass. 

Sojiro Sakura, the owner of the cafe, was tough on him. He agreed to take him in, doesn’t mind him as long as he follows the rules and avoids any trouble. 

It was Ren Amamiya’s first day of school, yet instead of Shujin Academy, he’s now inside a castle. 

And now, he’s locked up with a blond boy he doesn’t know. With a certain girl missing. 

He’s in a mess just now. 

They tried to escape, but the attempt was fruitless. 

From afar, they saw someone else; it was a man in a pink cape. 

The caped man, along with a few demons, approached the cell door. He had seen his face somewhere else.

“Kamoshida, is that you? Why are you dressing like this?” 

“I thought it would be some petty thief, turns out it was you and that transfer student, Sakamoto.” For some reason, Kamoshida wore a pink cape and a golden crown on top of his head. He has golden, shining irises. “So you brought a new friend? Pathetic, you can’t even do a thing yourself.” 

“He ain’t a friend, so let him stay out of this.” Sakamoto gets closer to the cell door. “And stop yapping, you asshole! This ain’t no joke!” Why are those demons being obedient to Kamoshida?

“Is that how you speak to the king?” He touched his chin, “For sneaking into my castle and insulting me, the king. You guys are sentenced to an execution.”

“Jack-o'-Lanterns, take him out!” 

Those pumpkin demons, or what Kamoshida called a Jack-o'-Lantern, entered the cell, and then a flame was on Sakamoto’s rib. 

“Just go! Get out of here, they are serious about killing us!” Sakamoto screamed out loud with all his might. Ren punched one of those Jack-o'-Lanterns in the hope of helping him, but they evaded instead. “Hurry up and go!” And then a Jack-o'-Lantern blocked his path, pinned him to the wall so he could not move. 

A punch on Sakamoto’s face. 

And another. 

And another. 

And another. 

And another. 

And another. 

……

Ren helplessly watched Sakamoto getting beaten up over and over again. Kamoshida hit his final blow on Sakamoto’s stomach.  

“A pest like you ain’t worth beating, I’ll have you killed right now.” 

Sakamoto is about to be burned to death. Yet I could only stand and watch. 

No. 

NO. 

“STOP IT!” Ren shouts it out loud without thinking. 

Kamoshida’s disgusting face approached Ren, “What, haven’t you seen enough of my power over this castle? The eyes in your eyes irritate me!” Ren lowered and pressed his eyebrows together, and the corner of his mouth went downward. Seeing his face makes me wanna puke. 

Kamoshida raised his leg. Pain pierced through Ren’s rib, his back hit the wall, and then he was grabbed by Kamoshida. Then his head is forced to face Sakamoto’s. The Jack-o’-Lanterns proceed with Sakamoto’s execution, and his face is filled with fear. 

“You will soon see the price of disobeying the king!”

 

 

 

The air froze. 

“This is truly an unjust game…” His eyes followed the path of a glowing blue butterfly. “Your chances of winning are almost none.” It spoke with the voice of a young girl. “But if my voice is reaching you, there may yet be a possibility open to you…” 

What’s the matter? Are you simply going to watch? 

A voice echoed through his brain; he had never heard of this voice, but the presence felt familiar. 

Are you forsaking him to save yourself? Death awaits him if you do nothing. 

Was your previous decision a mistake then?

Time stops flowing, and he sees the day he was accused of assault. 

That night, he was outside, seeing a man forcing himself onto a woman. 

He approached to save the woman, but the drunk man’s head hit the ground without a push. 

“Damn brat, I’ll sue!”

The loud ringing of police cars is getting closer. Instead of running away, the woman talked to him. 

“A kid like you shouldn’t mess with someone as powerful as him; he was the man who would steer this country in the future. You are here only to be crushed by his ark, as it should be.”

The woman he saved said this to him, and afterwards, she made a fake witness in favor of the drunk man who had just assaulted her. Marking a black spot on his record. 

They were the reason why he moved to Tokyo for his one-year probation. 

Ren thought about it. He faced the consequences, but he did not regret his actions. 

Even if another chance exists, he would still repeat the same decision as before. Regardless of who they were, people weren’t born to be prisoners to those corrupted authorities. 

It wasn’t a mistake!

He started to struggle, but many Jack-o’-Lanterns pinned him still.  

“I don’t wanna die!” He watched Sakamoto in despair. 

Very well… I have heeded your resolve. 

Ren’s head is going to explode; his head feels like there is something about to burst from it. And it is expanding larger and larger. 

Vow to me. 

I am thou, thou art I… 

Thou who art willing to perform all sacrilegious acts for thine own justice! 

Call upon my name, and release my rage! 

Ren cried out; his lungs went empty. 

Kamoshida’s grin went wider as the ghostly lantern started to swing like a pendulum. 

Show the strength of thy will to ascertain all thine own, though thou be chained to Hell itself! 

“That’s enough!” 

Kamoshida turned to him, “You wanted to get killed that much? Fine, you get what you want.” Ren’s glasses blew away from the punch on his face, and his minions were about to give him their final blow. 

Then, they crashed into the wall by his willpower; their eyes stayed on him in confusion and terror. Ren noticed there was something on his face. He put his hands on the external object out of instinct.

Ren started to rip his mask off, a layer of his skin was ripped away, and blood was splashed in the process. It was agonizing, but in order to feel free, it was worth the pain. 

Ren is facing Kamoshida and his minions, and he grinned. Uncontrollably going wild. 

His body was covered in blue flames; it was a metamorphosis. With sounds of chains, a figure was forming above him. Kamoshida could only crawl into the corner. And Sakamoto is watching Ren with his mouth wide open. 

I am the pillager of twilight—Arsene!

Ren looked at his hand, which was now covered in red fabric.

I am the rebel’s soul that resides within you. Ren gazed at Arsene, wearing a crimson outfit, a flaming mask, a hat with horns, and a pair of dark wings sprouting from behind. It’s an image of a gentleman thief. A demon. Or a fallen angel. 

If you so desire, I shall consider granting you the power to break through this crisis. 

It was an instant deal. 

“Give me your power.” 

Hmph, very well…

“Jack-o’-Lanterns! Start by killing that one!” The king of the castle pointed at Ren, and the minions obeyed. 

“Instant death, ho!”

Two of them roam in front of him and attack him with a fireball. 

Without panicking, Ren dodged all of it. 

Kill them however you want. Run wild to your heart's content! 

Before the enemies could even react, he took offense. Arsene manifests above him. 

“Eiha!” 

Red and black flame-like energy ran through a Jack-o’-Lantern from below, and it dissolved into glowing red particles. 

He jumped to the back of another Jack-o’-Lantern and stabbed his knife into the pumpkin. Inside the deep scar were glowing red crystals. Its head was cut in half and then shattered into pieces of crystal. And the crystal pieces dissolved into those red glowing particles. 

“You like that, KamoSHITa!?” Sakamoto bumped into Kamoshida, pushed him away.They locked Kamoshida inside of the cell. He held the bars tight, revealing that he only wore pink underpants underneath his red cape. With a swing, the keys are now thrown and washed away by water. 

“After them! Don’t let them escape!”

This place was like a labyrinth. They came to a dead end. No matter how many turns they took, they couldn’t locate her. At the same time, they also need to evade demons. Kamoshida was trapped, so Saika should be safe for now, right? 

“Blondie! Fuzzy Hair! Look over there!” On their left side was a weird-looking cat trapped inside a cell. “You are not demons who prey on Magatsuhi, right!? Get me out of here!” It pointed in a direction. “The key is right there.”

Notes:

Noted that the only OC in the entire fic is Saika Takao; all the other characters are from the other Megaten games. Mostly from Persona 5 and Shin Megami Tensei III: Nocturne.
It's a fusion fic, so there will be some changes to the settings and certain *super* minor characters.
There will be spoilers for both fandoms; you have been warned. Ships are eventual Sumire/OC and minor Ren/Akechi (to be tagged)
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The official artwork of Mastema in SMT series (by Kazuma Kaneko).