(flash back)
the day after left, Issei had started turning into a dragon slowly. His horns, elbow spikes and tail were slowly forming. His body was being transformed on a cellular level and no one said that it will be quick and painless. Issei was still emotional after everything that happened yesterday with Rias and the others and the physical pain was just making it worse, Issei was at the emotional threshold and decided to take a walk and eventually recognized a place that brought back painful memories. Issei ended up at the same place where the fallen angel Raynare killed him. To end up back where he started, from one hell to the next.
Issei: why? WHY ME? WHAT DID I DO TO SUFFER SO MUCH?!!!
Issei's power flared and Issei went berserk, he started to fire energy projectiles and ripped part the forest floor. Issei roared from pain and anger and his horns, tail and spikes grew quickly because the dragon's power flows through their rage.
Ddraig: Issei I understand your frustrations but you have to calm down before you fully transform into a raging dragon. It'll attract their attention.
Issei can't hear Ddraig at all and continued to destroy the forest, he created a massive fire ball and made a huge crater in the ground. Issei roared again with tears running down his face as he was still in all manners of pain. Issei eventually calmed down and just sat on the crater's edge. His mind was in disarray then suddenly felt calm, it was honestly a new experience for him. Only then did he register the sensation of two slim hands holding him from behind, one on his head and one on his chest, he expected his chest pain to flare up but it didn't happen.
Woman: don't move. I'm trying help.
Issei: why help me?
Woman: you're in pain. Let me help
Issei was conflicted, why would a random woman help him and what are her intentions? Should he let her? She did just calm him down and it felt good, he hasn't felt like that in years. If she wanted to hurt them then she would have done so already and he could defend himself if she tried anything. After deliberating Issei decides to give her a chance.
Issei: thank you miss...
Woman: Kuroka. My name is Kuroka now don't talk. Your mind is in disarray, your ki is unstable and your heart is running a marathon. I don't know what you went through to put you in such a dangerous state but I'll try my best to help.
Issei: thank you. I'm Issei.
Issei closed his eyes and Kuroka was using her sage magic to stabilize Issei which was working. Issei felt calm, his mind was clearing, his heart palpitations were becoming normal. After a few minutes, even the pain from the transformation stopped.
Kuroka: you'll be okay now but this was just a temporary fix, you'll need to sort out the cause yourself.
Issei turns around and looks at Kuroka, he notices her kimono, her two black tails and cat ears her golden eyes caught his attention the most. They both stare at each other and Issei snaps himself out of his trance.
Issei: if only it was as easy as it sounds.
Issei gets up and so does Kuroka,
Kuroka: do you want to talk about it?
Issei: no.
Issei goes and sits by a tree. Kuroka goes over to him and sits on his lap.
Issei: what are you doing?
Kuroka: full disclosure, when I saw you I felt something pulling me towards you and it wasn't just your power.
Kuroka was just the right size, she fit perfectly in his lap and cuddled him.
Issei was confused as to why, why would she help him since they just met. Why is she clinging to him and why can't he find the will to push her off?
Issei was too confused and yet he knew that she was here to comfort him, the one thing he longed for, Issei just hugged Kuroka tightly and she hugged back and both lay there till the sun set, both watched it go down together and fell asleep holding each other. Kuroka could feel Issei's heart beat and it brought her joy knowing that Issei is okay.
Issei and Kuroka would begin to spend time daily for a few months, Issei was still emotionally distant and didn't talk about his past. Kuroka didn't force him but she gave him a reason to trust her. She told him about her past.
Kuroka: I know you still keep your guard up around me and I understand but I want to earn your trust.
Issei: ....
Kuroka: 6 years ago my little sister Shirone and I were part of a devils peerage. Our master was secretly performing illegal and inhumane experiments on us to make her stronger. They were a success and he was about to perform them on my little sis. She was too little and there was no way that I would let that happen. I killed my master and his peerage, my sister and I ran since I was marked a stray. Eventually we were hunted down by Grayfia of all people and I knew that I was no match for her. I tried to escape with my sister but she managed to grab Shirone. I was no match and ran away.
Issei: does your little sister have white hair, short and has one cat tail?
Kuroka: yeah but how did you...
Issei: I know Grayfia and Sirzechs, they are the only kind hearted devils around. I used to be a pawn in Rias Gremory's peerage, your sister is a rook in that team. She's strong and she's doing fine but doesn't talk much. Has a stoic expression on her face most of the time. She goes by the name Koneko.
Kuroka is over joyed that her little sister is alright but then it clicked.
Kuroka: wait...what do you mean you used to be?
Issei: sigh.... You trusted me with your past. It's only fair that I do the same. Look into my memories.
Kuroka: are you sure? I'll be going right through your memories.
Issei: I have nothing to hide.
Kuroka: alright then. I trust you.
Kuroka puts her hands on Issei's head and closes her eyes, using magic she looks through his memories from his young age, hearing about his parents death, running from one orphanage to another and being abused, surviving on the street, having a light spear put through his chest, 5 years of being a pawn, being used by his master who knew about the fallen attacking him, being in a coma, revealing Riser's secret to Rias, her sudden guilt and kissing Issei, fighting Riser then removing his pieces and a massive red dragon surrounded by flames. Kuroka only saw glimpses of these but it was too much. Kuroka let go of Issei and jumped back, breathing heavily with tears running down her face.
Kuroka: JUST WHAT THE HELL DID THEY DO TO YOU?
Issei: what haven't they done?
Kuroka: I'll kill that bitch Rias when I see her.
Issei: as fun as that sounds you better not, you're still being hunted and it'll make things worse for us both.
Kuroka: I can't believe that she had the nerve to do that. To start loving you just because Riser hurt her feelings even after you loved her from the start. The fuck?
Issei: after all that you saw, that's what got your attention?
Issei deadpanned.
Kuroka blushed and stammered.
Kuroka: no no no you misunderstood. Well you see... I mean to say is that... UU
Issei cuts her off by kissing her on the lips. Kuroka's eyes widen then closes them to savour the kiss. She really did feel something for Issei and now she knows that it was love. Issei breaks the kiss after a couple of seconds.
Issei: I trust you enough to say that I feel something for you too and I think I just proved it.
Kuroka: yes. Yes you have, now more.
Kuroka and Issei made out for a long time.
( End of flashback)
Issei: I would use magic and disguise myself and sneak into town. Got a few part time jobs, used my cash I saved from my contracts and Kuroka stayed with me in my apartment since then and now here we are.
Kuroka just snuggles up to Issei and stayed by his side the whole time. Rias looked jealous as fuck.
Akeno: if you came into town daily then why didn't we notice your magical signature?
Issei: because I became a dragon. My very being has changed so that's why you couldn't find me. I could have walked right by you and you wouldn't have noticed.
Koneko: so that's why you left?
Kuroka: yes. I knew that you would be okay because lady Grayfia was kind enough to protect you. I could tell by her aura. Strong but compassionate.
Issei: she's right.
Grayfia: you're too kind.
Koneko: that explains why you didn't visit in 5 years.
Kuroka: I was a stray. I was being hunted. If I showed up then you would have been found out and used against me.
Sirzechs: miss Kuroka, you said your master experimented on you. Please shed some light that subject because I was led to believe you went berserk.
Kuroka: of course. It's the least I can do. Back when my master was experimenting on me, I saw him take notes of everything he did and kept them in a item that he hid in plain sight. I wanted to show it to lady Grayfia that day but she was gunning for me and any action taken that didn't result in my survival would have been the death of me.
Grayfia: your master was a friend of our family but we never knew of his actions and I was too angry at you to think rationally. I should have tried to look beyond my anger. I am sorry.
Kuroka: no need to apologize. I hope you forgive me for killing your friend. I had no choice.
Grayfia: you saved Issei's life. How could I not?
Sirzechs smiled.
Sirzechs: so you mentioned that he kept his research hidden and you know where it is. If you provide that you'll clear your name.
Kuroka: I would love to. She has it.
Kuroka pointed to Koneko. Everyone looked at her confused who was just as confused.
Koneko: how would I have his research?
Kuroka: your hair clip. The one with the black cat on it. The research is hidden.
Issei: he picked one hell of a hiding spot.
Kuroka: yeah my master Shalba was quite clever but too power hungry.
Sirzechs: Koneko would you be so kind to give us the research?
Koneko: yes sir.
Koneko gives the hair chip to Sirzechs.
Sirzechs: interesting. There are dozens of seals planed on it to prevent the content from being viewed. This will take a long time to break. Ajuka and Azazel can help. Everyone here can continue enjoying themselves. I have work to do. Take care.
Sirzechs teleports away and Grayfia follows.
Everyone else just continued to enjoy themselves.