10 years ago…

Everywhere around Rias Gremory was scores of corpses littered around the dark, desolate street of some city. At the age of seven she was already one of the most feared devils for her organization, Khaos Brigade.

The smell from the smoke coming from the nearly destroyed corpses and blood filled the air as Rias stood there, disgusted at both the smell and herself, "I'm a monster." She muttered lowly with her hands covered in blood.

Her organization had many connection with many factions as the result they had many members. Like Rias there were many of members were still children but they were forced to handling many task in order to raise the fund of organization and expand it.

In Rias case's, she had to eliminate as many as enemies of the client and became a weapon for war.

Those devils were the 10,510th to 10,910th batches of corpses.

Even though they never said a single word to her but she knew that those corpses were her kin from their wings.

Because of her carelessness that they could kidnapped her, Rias was forced to become a leader of small group called 'Gremory' Group named after her family name in order to ensure Sona safety. Since they threatened that if she didn't do what they told than they will kill Sona like what they did to her maid.

Being the leader and the only member of 'Gremory', she was usually tasked with requests from clients. However, all of them required killing in some form. A monster out and out, as Mikoto would view herself as.

Rias looked at both of her hands. Although it was soft and clean cause it was washed by rain, but many people had died by the power of destruction that she emitted from those hands.

"Nothing can wash my sins away." She murmured to herself as she let the rain soaked her face. From the corner of her eye, she noticed a demonic powered gun. Rias stared at the gun for long time.

She had enough of this life where killing were a daily necessity. "Maybe I should just disappear from this world." She said to herself as she took the gun and pointed it to her head. Half of her was shocked at her incredibly rash decision while the other half was happy that she no longer had to suffer anymore.

"I'll end all of this with my death." Rias said as she closed her eyes, ready to impale herself with the sword at any moment. Before the darkness could consume her permanently, a voice sharply pulled her back to reality.

"Oi, its too early for you to die, you know." The voice said as Rias turned to behind her to see a boy with short brown hair standing around 1 meter from her place. Due to the faint lighting from the street lamps, she could not make out his face clearly.

However, Rias could clearly see that he was not at all pleased with what she's doing. "This is my life! I'll do what I want with it!" She roared as the boy sighed.

"Your life does not only belong to you. What about your family? Your friends? They'll be upset if you died just like that." The boy explained in bored tone.

Family? Friends? Ever since she got involved in the Khaos Brigade, such concepts no longer existed in her world.

Deep down inside, she did wish for everything back to that time.

Back to when she still lived with her family.

Back to when she liked to play with her older brother and his wife.

Back to when she still played with Sona and her sister Serafall.

Back to when she still innocent about this vast world.

Even for a 7 year old prodigy who feared as 'The crimson chaos heart', this was too much for her.

Rias dropped her hands as she trembling in anger, "Shut up. You don't know anything." She said with her crimson hair closed her eyes.

"You were forced to kill all those devils? Right?" The boy said in sad tone as Tears filled her eyes as she started trembling with anger.

"How did you know that?" Rias pointed her hand toward the boy, "Answer me." She said as she released the torrent of black energy.

The boy took a step back, shocked at the girl's action.

All of the corpses had a devils wings. Any idiot would be able to figure out that they were all devil, and that the girl had killed all of them because she was the only person here other than himself.

His legs started to shiver a little, however, the girl was too consumed with fury to notice any of this. "Answer me." Rias hissed under her breath. The boy remained silent. He was afraid that the girl would kill herself if he said something wrong.

"Answer me!" Rias roared as she released a beam of power of destruction toward the boy. The boy clicked his tongue as he raised his left hand that now covered in red dragon-like hand gauntlet. As if that was just a small attack the boy punched the beam to destroy it with his red energy.

Enraged, her body covered in black cloaked as she let the power of destruction to pour out from her body like a fountain and she redirected all of this towards the boy like a roaring black tsunami who only made a big red magic circle and punched through it.

Magically the red energy from the boy and the black energy from Rias clashed and destroyed each other. "Tch, Draw…" The boy murmured under his breath.

The boy raised his palm as he showed her the green orb on the back of his left hand, "If you still want to fight than I guess I will handle you." He said as the green orb shining.

BOOST

Rias looked at him, dazed and confused since she didn't know that her knight in red armor came to save her now.

"Hey hey, tell me your name!" Rias yelled while chasing after the brown haired boy. They were currently playing in park.

It was a sunny morning and the birds were chirping loudly as the both of them enjoyed the peaceful scenery while playing together.

While she was still trapped in the organization but the boy apparently already destroyed half of the organization alone, he promised to free her from all of this. Apparently, Khaos Brigade still as strong as ever with hero faction and their secret weapon.

The boy thought for a minute and smiled, "I already told you right I am the current Sekiryuutei!" He said in proud tone.

"That's not a real name! Just tell me your name!" Rias shouted as the brown haired boy chuckled and ruffled her hair.

"It's even more rude of you to say that its not a real name. All my dead comrade really like that name you know." The boy said playfully as Rias looked at him with confused eyes. Meanwhile, he took out a little bracelet and placed it on Rias's hand.

"Well, I got this from a Gachapon machine….. Ahh, I don't really have the money to get you something nice, like a locket or something, but I hope you like it." The boy said with his hands on the back of his head. Rias's cheek flushed bright red as she admired the bracelet resting in her palm.

Annoyingly beautiful that bracelet, "Thanks." Her voice down to whisper level

Then they heard someone called Rias as the boy got up and stretched himself, "Well it looks like Sirzech-san already coming it will be better if I go now." He said as Rias grabbed his shirt.

"Do you really have to go...?" Rias asked with sad face.

She wanted the boy to stay with her forever and ever, just like now with the two of them sitting under a tree and enjoying each other's company. But he was insistent in freeing her from the darkness. Or perhaps he had gotten himself too far down into danger when he stopped the organization and so the only way left to go is to free her completely.

"If you really want me to come back faster..." The boy paused for a moment and got an idea, "then work harder to had your own peerage because I will certainly come back to find you once you had one for your own."

"Ah..."

The boy squatted in front of her and held a pinky up, "Promise?" He said with foxy grin.

Rias smiled and hooked her pinky together with his, "Promise!"