Disclaimer: I do not in any way shape of form own Blue Exorcist all right belong to Kazute Kato and Shueish publishing company now with that out of the way summary time

As well this is my first ever Fan Fic so please be light on the flames and I'll try to have fairly regular updates.

Anyone who has seen the anime or read the manga will remember the flashback Rin had to when he was about seven years old and broke Father Fujimoto's ribs. This story is a slight AU where instead of just being a very severe temper tantrum was actually when Rin's demonic powers awakened. As well, Yukio hasn't become an exorcist because he never received a mashou from Rin. So as well the twins have kind of switched places with Rin being and Exorcism teacher and Yukio being the exorcism student.

Chapter One: The Awakening

Father Fujimoto/Shiro's POV

"Rah" that was the first thing Father Fujimoto heard as he stepped into the elementary school classroom. The next thing he heard being the scared screams of both the teachers and students. As soon as he stepped into the classroom he saw the reason; his own adopted son Rin was having another tantrum. However what set this tantrum apart from all the other was that Rin had a small amount of blue flames licking around his shoulders and crown of his head. As soon as Shiro saw those flames his heart seized up. He knew that if any of the other people in the classroom had a mashou they would only be freaking out even more. Because these blue flames were of Gehenna he knew that they shouldn't be able to see them, nevertheless it didn't make those flames any less dangerous. He immediately got Rin's attention by shouting his name, "Rin!" This had the desired effect as soon as he said this Rin's attention snapped to him and quickly took on a guilty look. Seeing this Shiro continued, "Is this how you want people to think of you as a bratty misbehaving child with no self-control?" Rin quickly looked even guiltier but still defended himself, "But they started it by picking on Yukio and calling me a Demon's child, I even heard a teacher say that!" Shiro then proceeded to find Yukio in the crowd of kids and ask him, "Is this true?" Yukio slowly nodded his head yes and immediately Shiro understood why Rin was acting this way; however this did not mean Shiro was going to condone this kind of activity. "That clears matters up Rin, however that does not give you the right to act like this. You could have seriously hurt someone like this." Finished scolding Rin, Shiro turned to face the teachers, "And you, you should be ashamed of yourselves. Not only did you not protect Yukio from being bullied, you also let the students pick on Rin's insecurities about being called a demon and even agreed with them. So from now on neither of my sons will continue to go here after this day, and you can expect me to send in a full report of what happened to the principal and any other person who outranks you. Come on you two we're going home."

Time Skip About One Hour

After arriving back at the monastery Father Fujimoto sent Yukio while pulling Rin aside to talk to him in private. "Rin when you rampaging back at the school did you notice the blue flames around you?" Shiro asked Rin once they had made it to the kitchen. Rin quickly looked up at Shiro in surprise and replied, "I thought I was just seeing thing but now that you saw them too, yeah I did." When Rin confirmed that he had seen the flames Shiro visibly paled. Thinking he had done something wrong Rin quickly started apologizing, "I'm sorry dad I didn't mean to all I remember is getting mad and suddenly they were just there." Seeing Rin apologizing for something he couldn't control quickly snapped Shiro out of his own head "No you don't need to apologize it's my fault I should never have kept who your real father was from the two of you." Hearing Shiro say this caused Rin to lose his guilt and become filled with two entirely new emotions: anger and surprise. "Wait you knew who Yukio and I's father was and you never told us!" shouted Rin angrily. Shiro not really surprised by the boy's outburst simply nodded. This cause Rin to be filled with even more rage, "so who was he then some deadbeat who couldn't hold a job or afford to keep us!?" At this Shiro replied, "Before I answer that question answer me this do you remember any of the Bible stories I told you and Yukio when you were a little younger about how demon and Satan came to be?" Surprised by this Rin nodded that yes he did remember, figuring he wanted him to tell the story to make sure he knew Rin said, "Satan was originally an angel who was God's right hand man until one day he got fed up with God thinking that humans were superior to and betrayed God who eventually found out about Satan's betrayal and threw him from heaven." After Rin finished Shiro nodded his head, "Good you did pay attention, but what you don't know is that those are real stories and demons and Satan are real, and you Rin, are the illegitimate son of Satan himself." Shocked by this revelation Rin was left completely speechless. Sighing to himself he turned away a told Rin, "follow me." After being told this Rin scurried to catch up with Father Fujimoto. Taking them into the front area of the monastery Shiro took a set of keys from his necklace and unlocked a secret door under the podium and calmly walked down into the room beneath. After seeing his adopted father go down into the room he followed after though a little more hesitantly. When they reached the bottom of the stairs all Rin could see was a fairly large storage chest. Shiro quickly walked up to the chest and took out yet another key and fitted it into the lock and twisted it. Inside the chest was a single item; a blue about 1 meter long katana. After taking the sword out Shiro then preceded to hand it to Rin and explained, "This is the demon slaying blade Kurikara. The day you were born your demon heart was sealed in this blade allowing you to live a fairly normal human life until now. Though now it seems that the seal is no longer strong enough to hold back your demonic abilities. Never draw this sword; the moment you do your demon heart will become free and you will never be able to live as a human again. As soon as your flames were first released I lost a wager with a friend of mind that stated he would let me raise you as a human until your demonic abilities broke past the seal now that they have I have no choice but to follow through with the agreement which was if your powers ever broke the seal I would have to let him raise you as his ward." After absorbing all the information, Rin was immediately angry again and shouted at Shiro, "What kind of father bets their son? Now you're telling me that I have to go live with a friend of yours that I may have never even met. What the hell is going on here!?"

Shiro having expected this kind of reaction calmly said, "We don't have time for this, my friend put a charm on the seal so that as soon as it was no longer adequate in holding back your flames he would know he is more than likely on his way here now." Rin at this answer simply just looked stunned and said to Shiro, "Is it because of how I acted today? Because if it is I promise I can change just please don't send me away!" at this point Rin was flat out sobbing and begging for Shiro to let him stay. Shiro having heard this was completely heart broken and with tears in his own eyes said, "I'm so so sorry Rin but this is out of my hands even if I refused to give you over he would just easily take you anyways. If I could keep I would and never let you go but simply can't you have no idea how much this hurts me to do this." After saying this both Shiro and Rin were crying uncontrollably. Shiro then scooped Rin up into his arms and hugged him until Mephisto arrived. When Mephisto arrived at the monastery he found Shiro sitting in one of the pews still holding a now sleeping Rin. As soon as Shiro saw Mephisto he immediately begged him to let him keep Rin but Mephisto would not let Shiro out of the deal in any way. As a last ditch effort to still have contact with his son he asked something of Mephisto, "If I can't be allowed keep Rin as my son can you promise me that you will train him to control his flame and become an exorcist, and that I can at least come and visit him every so often?" After weighing his options Mephisto agreed on one condition, "You must never tell the other twin, Yukio where his brother and you cannot tell him about the demon world." Seeing as this was the only way he would ever see Rin again Shiro quickly agreed to the terms. And with that Mephisto took the still sleeping Rin and had his driver take him back to his mansion at True Cross Academy.

End Chapter One

Author's Notes

Whew 1648 words that is a lot for a new time author if any of the characters seem to OOC tell me and I'll do my best to fix it. On a side not seeing as how Yukio can't be the anti-demon pharmacology teacher I'm going to have Shura replace him as in the manga it is said she is a doctor meister. And as always review and tell me of any suggestions and mistakes I may have made.