Another insane idea of mine. This time though I'm not using OCs, just stuff I stole from a certain game series by Eushully. Stole, modified, and yeah, you know, things like that. The main character will be Issei and yeah, I'm not pulling your legs this time. It will be Issei and not Xenovia… really.

Disclaimer: I do not own DxD or the Ikusa Megami series of eroge.

Chapter 1: Across Time

-4500+ years ago-

"Milady."

Celica look up to the sorrowful face of his goddess, the woman whom he had sworn to give his all to, and in return she gave her all to him. Unfortunately, their love was doomed to fail with him being a human and she being a goddess, especially due to what he had done for his goddess.

"Celica… I'm sorry, I cannot convince Zeus of your innocence."

"It is alright milady. As long as you live then I am content."

"You slew Chernobog, one of the two high gods of the Slavics. Zeus is afraid that you may do the same onto him."

"…I understand. I am a human that had killed a god, I am an existence that cannot be forgiven by the gods."

"Celica."

The red haired goddess cried as she touch the hand of her human lover. Astrea has always been close to humans and of everyone she had met, no one caught her attention as much as Celica Sylphil. As a goddess of innocence and purity, all her worshipers are women. But Celica is the only male of that age who worshipped her. A wandering warrior who was betrayed by the one he worshipped and was found by her. As a result, he became her worshipper… and more.

She who was once a virgin goddess gave herself to a human of all thing. If that did not enrage the gods who had tried to court her, then what Celica did had certainly made Olympus rage. Becoming a godslayer, even if it was done in her defense. Astrea cannot accept it. Just because the gods are afraid of a human who could kill a chief god does not mean Celica could be treated like this.

"…I swear to you Celica, by my name I shall not allow you to die."

"Milady?"

Fire began to burn in the goddess' blue eyes. She rose from the cold stone floor and march out with determination. Few would help her to free Celica, and fewer still would are free to even give her aid. But… she knew of one deity who could help her, a god who above all loves humans as much as she does, the strongest God of all.

At that day, the Goddess Astrea went to Heaven to pay the Biblical God a visit.

-Celica's execution-

Astrea was not present as the gods brought the bound warrior to be executed. Unlike what was done to the likes of Prometeus and Loki, Celica will be given a swift and absolute death, reaped by Hades himself. Few questions why she's not present though most concluded that Astrea cannot bear to see her human lover being executed.

Then Celica was brought out dressed only in rags and chained with chains similar to those that bound Fenrir, the Norse's godslaying wolf. The gods figured that it's only fitting to treat him the same as the Norse's wolf.

Celica's execution ground is shaped like an amphitheater with an altar in the middle where Hades awaits. The Greek God of Death looks as menacing as usual with his non-existent eyes peering into Celica's. He carry with him an enormous and elaborate scythe that he would use to reap his soul. Any lesser human would've trembled in fear just from the sight alone, maybe died on the spot with how menacing Hades is.

But as expected of a godslayer he does not even flinch in the presence of so many divine beings and Hades. He proudly walk up the stairs leading to the altar where he will be executed. He even dared to smile.

Many gods takes this as a sign of arrogance. But this is not an arrogant smirk of a madman as they thought it is. This is, what only Hestia, the Goddess of Hearth and Family recognize, as a victorious smile of someone she's familiar with, someone close to Dike. At this moment, Hestia look behind her and hear the sound of a familiar footstep running.

"Do it."

Zeus ordered Hades once Celica was placed on the altar and bound. Hades lifted his scythe and peer into the godslayer's eyes. He has to admit that he could respect Celica not flinching at all in his presence and even accepting his death like this. Plus he hates the other pantheon. If one of their own kill a god from another pantheon in defense of one of their own, Hades would more likely reward them for their service. Alas he's not the one in charge. At least he would make it quick for Astrea's warrior.

"Any last word boy?"

"…"

"Nothing? Very well. If it makes you feel any better, I'll be waiting for you in the afterlife and I promise to take good care of you."

Hades said. The moment the scythe was swung down, someone knocked down Hestia. Her red hair disheveled and her face wet with tears. Goddess Astrea had arrived… but Hestia who is now looking between the two lovers knew differently. The moment Hestia saw her, she knew.

As Hades' scythe cut off the godslayer's head the crowd began to cheer loudly. But one voice wailed calling out an unexpected name. It is a wail only heard by Hestia who is beside said person.

"Astreaaa!"

-Present day, Gremory vs Phenex Rating Game-

"Guhaa!"

Intense pain attacked Hyoudou Issei as he lost count of how many times he had been knocked down only to stand up once again. He swore he would win for his Buchou. But Rias Gremory was already on her knees and wasn't trying to stand up. She ran out of her magical energy. She hit away Raiser countless of time, but Raiser kept on resurrecting while spreading his fire. As if nothing happened. He needs to stand up and protect her and Asia.

Raiser's fist went deep into his stomach and twisted, causing him more immense pain.

There was blood coming out of his mouth. His eyes became blurry and he felt dizzy. He could barely stand and his feet are unstable. But still he tried to fight. The battle progressed to its climax.

Rias Gremory, have no more moves. In other words, checkmate. There is no one in her peerage who has any strength left, including herself.

But that boy continues to stand up.

Issei.

He is the only one who continues to move forward towards Raiser even in this situation. However, it's over. Even if he stand up once again, Hyoudou Issei has no strength left to fight. Sekiryuutei or not, he's no longer capable of fighting. Only a miracle could overturn this fact that Rias Gremory had came to accept.

'Do you want this to end here boy?'

A voice. Hyoudou Issei heard a strange voice as his consciousness blurred. It is a voice that he could hardly tell if it belongs to a man or a woman. But nonetheless, he instinctively knew that this voice will be his only chance to achieve victory, to safe his buchou, his beloved Rias.

'No, I will not let this end here. Not now, never!'

'But you have no more power left. Even with Boosted Gear, you cannot win boy.'

'I know. But that doesn't mean that I will give up!'

'To fight for the love you believe in?'

'Yes!'

'What will you sacrifice to fulfill this wish? What will you sacrifice to win?'

Issei paused at this question. What will he sacrifice to win? What will he do? Can he even win? No, the voice is offering him something. If all those games and movies he saw are right, then this voice is offering him power at a deep price. The question is, how much is he willing to sacrifice for Rias? For him, the answer is obvious.

'…everything, even my soul.'

At his answer, he could somehow imagine the owner of the voice grinning.

'You're really wasted on someone like her. Very well, if that is what you're prepared to offer then I shall reply in kind. I shall fulfill your wish, Hyoudou Issei. Now sleep. The next time you awaken, we shall become one.'

Somehow feeling like he could trust the voice, Hyoudou Issei closed his eyes. At the same time, Hyoudou Issei's body stood up once again, this time different as his body is surrounded by a strong aura. The Phenex and Rias were surprised by this sudden turn of event as Issei's wounds began to heal and when his eyes shot open, it held no more kindness and naivety but instead the hardened red eyes of a warrior.

"Hmm, this is pathetically weak for a devil. Haishella would be disappointed. Still, this might not be up to my standard but this would do for now."

Issei (?) muttered to himself so that the only one who could hear him is Ddraig. The Red Dragon Emperor is the one who immediately knew that someone had replaced Hyoudou Issei. As the being sealed into his sacred gear, Ddraig has a connection to Issei's soul and the moment he felt the different soul, the dragon was shocked beyond belief.

[You… it can't be.]

'Heh, nice to see you again, Ddraig.'

Ddraig cannot believe who is currently in control of Issei's body. But… if it is indeed him, then the Phenex is as good as dead.

'Well I'll talk to you later. We have a fried chicken to take care of.'

[…true. Very well, let's see if you're still as powerful as you were back then, slayer.]

'Pfft, obviously not. This body cannot handle what I used to do. But against a wet-behind-the-ear Phenex? This should do. Ddraig, I'm feeding you my magical energy, how long can we maintain a balance breaker?'

[With your power? sacrifice the arm and I can guarantee you a full hour balance breaker. You don't even need to sacrifice anything. Your power is already potent enough, godslayer.]

Issei (?) show a ferocious grin after hearing what Ddraig said. A full hour? He could crush the Phenex in less than twenty seconds barehanded. Five seconds with his trusted sword, even less than that at his prime. But he is currently playing as Hyoudou Issei and he will do what he can with what Hyoudou Issei could supposedly do.

"So you still have some fight left in you. If nothing I should commend you for your tenacity, Sekiryuutei. But it all ends here. Yubelluna!"

Riser ordered his Queen to strike Issei down.

[Welsh Dragon Overbooster]

The Boosted Gear flashed with Ddraig's proclamation… and Hyoudou Issei disappeared.

"What, where did he… Aaahh!"

Yubelluna did not even manage to prepare her spell when suddenly her devil wings are ripped apart by Issei in his scale mail. After ripping her wings, Issei clench his fist that is covered by lightning and punched the Queen in the face. Unbelievable amount of power coursed through his hand as his fist made contact with Yubelluna and the Queen was blasted into the old school building like a falling meteor.

Everyone, including Ravel, Rias, and Riser gaped at the display of strength by Issei.

"R-Riser-sama's Queen retired."

Even Grayfia cannot believe the sudden change in Issei's power level. The dragon did not stop there as he immediately rushed towards the younger Phenex faster than the young devils could perceive. At one moment he's far away, in another second he's already in front of Ravel with a dragon shot ready. Ravel doesn't even have time to scream as she was hit by the dragon shot at point blank range.

"Impossible. How can my peerage be…"

Just like before, Issei suddenly appear in front of Riser. But Riser being the most powerful and experienced out of everyone in the field (sans the current Issei) managed to block Issei's full powered punch. Riser's hands broke but was immediately regenerated by his flame.

[As expected of the Phenex flame. Even I will have trouble finishing you off with this kid's body.]

Ddraig's voice echoed throughout the rating game field. Rias widened her eyes when she heard the dragon spoke and not Issei.

[The kid sacrificed quite a lot for me to do this. It's been a while since I personally fought. Now then Phenex boy, shall I show you that the Red Dragon Emperor is not all about power?]

'Good Ddraig, let them think that the sudden boost in power is you making a deal with Issei.'

Issei (?) thought as he continue to punch at Riser, breaking his bones with each strike while the Phenex is doing all he can to keep up with the dragon's speed.

"No one told me I'll be fighting the Red Dragon Emperor himself!"

Riser cried out as Issei knocked him down and crushed his head. It took him ten second to regenerate and Issei still kept punching him. He didn't even care about the Phenex flame that is trying to burn him. A small trick he learned long ago is that he can create additional barrier right on top of his skin for added defense against magic and even if Phenex flame can burn a dragon's scale (with the exception of some stronger dragons) the additional defense coupled with Riser being an immature Phenex made his flame harmless to the current him.

A right hook, a jab to his throat, kneeing him in the face, Issei dealt all kinds of damage to Riser without giving him the chance to retaliate. It is a one-sided beatdown. Riser is strong, but as strong as he is, he possess one weakness that is rather common to high-class devils of their age. Over-reliance on their magic. As a result, when facing a master of close quarter combat that has technique, speed, and power he cannot keep up with, Riser is unable to retaliate.

Ten minutes, twenty minutes, thirty minutes, Issei showed no sign of stopping the brutal beatdown of the Phenex although everyone thought that the one fighting is Ddraig himself. He purposefully did not use dragon shot or any other magical technique to defeat Riser. He could've ended the battle long ago but the satisfaction of beating up an immortal is too good to pass up, especially someone as arrogant as Riser. By now, Riser's mind had been broken, being unable to do anything but take the beatdown from the Sekiryuutei. His regeneration is already at its limit. Seeing that he should probably stop before he really killed Riser, Issei lifted him up with one hand and spin kicked him hard, breaking his backbone in the process.

"Riser Phenex is unable to continue. Victory goes to the Gremory peerage."

'Well guess that's it.'

[Hmph, it's always impressive seeing you fight. I am once again reminded why you're the only human I ever respected and even after that 'incident' you continue to surprise me even now, Celica.]

-Olympus, Hestia's home-

Librascale, the sword of Astrea has been kept by Hestia since her death, the death of the original Astrea executed as her lover by Hades himself. No one but Hestia knew the truth and it is something she will never speak to anyone ever.

The thin rapier-like sword is stabbed into the floor in front of Hestia's bed so she would never forget about the sacrifice Astrea made for her love and Celica who in turn also died for what he believed in.

Hestia woke up as usual after a well-deserved nap. But this time she woke up not to find the Librascale staring at her coldly but to find that the sword is emitting warm golden light. The Greek goddess of hearth bounced from her bed and land inches in front of the sword.

"Librascale is… coming alive again? Can it be? Astrea? Celica?"

The goddess wonder. The Librascale that had lost its luster after Celica's demise in Astrea's body had started to regain its warmth once again. The blade of judgement once again came to life. What can this mean? No, she knew already what this meant. Its master has returned. The question is, which one?

Long story short? I took Ikusa Megami Zero's setting and squeezed it into DxD. I just use a random time so it would seem that Celica is very old and reasonably obscure. Now, Celica took over this chapter but Issei will return in the next one, I promise. I only took Celica, Astrea and their tragic love story from Ikusa Megami. The rest of this story will be pure DxD… except maybe 3 or 5 more characters that I might steal from Eushully for this story. Obviously one of them would be Celica's faithful sword but the rest is… still in consideration. Cannon events will be thrown out the window after Kokabiel arc. Harem will be there but the main girl will be Astrea's reincarnation, NOT RIAS although Rias is acceptable as harem member and for once Xenovia is not a main protagonist.