Disclaimer:
I DO NOT OWN HATARAKU MAOU-SAMA or AO NO EXORCIST, if I do, there will Rin would be an antagonist.

Chapter 1

Rin Okumura walked with Kuro, Yukio and Mephisto on Hatagaya, as they were called to investigate the Seven Mysteries of Sasahata North High.

"Mephisto... Why do you have to come? Kuro and I are more than enough." Rin boasted with a large grin on his face. "You too, Yukio."

"Brother, we're here to give you advice, and some guidelines, as well as to watch over you."

"... What're you sayin' Yukio? They still don't trust me don't they? It's not like it's anything new... Though... Why Mephisto? Isn't he a demon as well?"

"A demon allied with the exorcists if I may correct you, Rin!" Mephisto said, with a smirk.

"Right, right, whatever! Anyway, what're these seven mysteries anyway?" Rin said raising an eyebrow.

"A forbidden classroom, the northern staircase has a different number of steps depending on if you walk up or down, the bloody Ninomiya Kinjirou statue walks, the sculpture in the art room grows double eyelids at 3 AM, A dictionary in their library has the word "curse" highlighted in red, piano in the music room stops playing the C note." Mephisto said, earning a look from the Okumura twins.

"Um... That's one mystery short." Rin said, putting his hands behind the back of his head.

"No one knows what the seventh is, cause supposedly you get a call from hell if you find out."

"Ah, so Satan has a phone? Don't tell me he has a Facebook account, or a Twitter as well?"

"Brother, do you have those accounts?"

"Nah, I don't like it anyway, and I don't want them commenting on my ears."

"No he doesn't. I'm sure, our father won't have the time for such things! He's busy conquering a certain world, called Ente Isla."

"What did you say, Mephisto!?" Rin said, worried about the inhabitants. "Does the Vatican know about this? We must send help to kill that-"

"Is that true, Mephisto? Where is this Ente Isla? We must help them eradicate the enemy as fast as we can!"

"Rin. Yukio. There is no other means to travel between worlds." Mephisto said, but he was the reason as to why Satan ended up on Ente Isla. He invented the "Gate" that Satan, Alsiel, Lucifer (to whom Satan named his son, the King of Light, and leader of Illuminati), Adramalech and Malacoda used to go there. He also thought that magic to his father, and hoped that being the careless demon lord he is, he didn't drop the paper that holds the incantation after he memorized it.

"Worlds...?" Rin and Yukio said in unison.

"Yes. He is currently in a world different from this, an Alternate Universe, actually, discovered by yours truly! The King of Space and Time!" Mephisto's grin widened at the moment Yukio pointed his gun at him.

"You're secretly still working for Satan, aren't you, Mephisto!?" Yukio said. "You're spying for Satan."

"How rude of you to make assumptions, Okumura-kun. You do know that I, helped you guys many times. Why would I do that if I'm still allied with my father."

"Let's just pray you wasn't." Yukio said.

"Um, enough for the tension, you two. Mephisto's on our side. I believe him. I have to believe him." Rin said then looked at the two still looking at each other.

Rin! I see some fast food! Let's eat there!

Good idea, Kuro! Rin smiled at the cat, and faced his brothers. "Yukio, Mephisto, it's going to be a while till dusk, so what do you say if we eat on... Ummm... SFC or MgRonalds?"

"MgRonalds. I feel something uneasy on SFC." Mephisto said looking at the outlets.

"Yukio, are you okay with that?"

"It's fine brother. I'm getting hungry anyway."

"All food on me!" Mephisto said and walked towards the fast food, in which they lined up. They have decided on their orders and when their turn came, the teenage guy standing on the cashier's eyes widened. His eyes were orange with slits as pupils, and his hair was teal, with a little hint of black.

"Samael? What are you doing here?" The guy said. The girl on his side looked at the guy in the cashier.

"Maou-san... Who's this?" The girl said.

"Samael..."

"How do you know my name!? We're going to talk about this outside... Not here with this exorcists, devil..." He whispered. What's this? Why would father tell his sons about my name and how I look!? Yeah! I'm sure this Maou-san is my father's son! But among all the children, it seems he got the looks of a younger version of father.

Maou shook his head. "Welcome!"

He looked at Rin and Yukio, who was looking at the menu. "Go find seats, I'll take the orders!"

"I want the Double pounders MgBurgers okay! And the fries too!" After Rin and Yukio said their orders, they left to find seats. Luckily, Mephisto was the last in line, so no one was in the back.

"We can speak in low voices. How did you know me?"

"Have you decided on your order, Samael?" Maou-said, in a cute and innocent voice.

"Stop calling me that!" Mephisto said and he earned a look from the girl in the other side of the counter. "We need to talk outside. You! Woman, here's the food I want to order..."

"Will it be a take out then?" Maou said, still keeping the innocent voice with his eyes closed.

"Whatever! Just come!" Mephisto said and then he wrote in a paper what him, Kuro, Rin and Yukio wanted.

Outside...

"Speak! Why do you know me!? Are you Satan's spawn? You look exactly like him."

"It's me... Satan. Your dad."

Mephisto examined the teenage boy from head to toe, sweating heavily. "What...did you...say?"

"I'm the Demon Lord, Satan. If you don't believe me, I can call Ashiya, or Urushihara... Or even Emi."

Mephisto's current state of mind. "..." His esteemed father, King of Hell, Lord of Demons, God of Gehenna...working as a fast food crew... It would be alright if it was a normal human... But... A Great Demon Lord Satan. That snapped. Mephisto fainted on the spot.

"SAMAEL! WAIT DON'T FAINT ON DULLAHAN II! DID YOU KNOW HOW MUCH ANOTHER BIKE COST!? SUZUNO DIDN'T EVEN COMPENSATE FOR IT! HEY! SAMAEEEEEEEEEEEEEEEEEEL!" Sadao Maou said, shaking the unconscious King of Time.

EDIT: SORRY! I DIDN'T KNOW IT TURNED TO THAT KIND OF MARGIN= SOMETHING... I'M SO SORRY! ANYWAY HERE IT IS.