"It's nice to meet you, Dad."
Everything falls into place, the red hair, his resemblance to you. This guy is supposed to be your son? Inevitably, there are a lot of holes in this story that ignite an immediate scepticism within you. "Wait a second, what do you mean 'Dad?' I'm not even married to Rias – and I'd sure as hell know if I got her pregnant somehow. I wouldn't hear the end of it!"
"You're right. Devils don't grow any faster than a human does, so how do you think a twenty-something year old version of your son is running around?"
"…Time travel?"
He snaps his fingers, "Bingo, got it in one. Sorry for showing up unannounced and all, but I needed to make a dramatic entrance to save your skin back there."
You frown, "I don't need your help."
"Prideful as always. I know, everyone is in good hands with the 'Incandescent Devil-Emperor' here. Even though this is an… early version of yourself – before a lot of important things happens to you. But you don't have a way to beat Vali at the moment."
You double take, "I'm called what?"
"Devils really love elaborate nicknames," he laughs, "For example, in the future you're regarded under several different titles. Aside from the Incandescent Devil-Emperor, you're also known as the Ruin King, the Mirror-Holder, the Shatterer…"
"Okay, we get it," Mitsuru interrupts before he can reel off any more of them. She seems to be taking this news a lot better than you are at the moment. You're a devil AND a father. "You were the one who broke into the lab a few days ago. Why?"
He shrugs, "Good old Dad here told me to leave that paper with you."
"I did?" you repeat, "You mean 'me' from the future?"
"Correct. Utilizing advanced technology and some devilish magic, we're capable of sending people through time. It was essential that I came back here, to this specific time, to give you this information."
"The form change system," Mitsuru continues, "You want me to complete it."
It's true that his assistance has resulted in the development of a new weapon. But the arrival of this imitator doesn't bode too well for your chances. She can summon equally powerful foes to try and take you down, if she can get over her personality quirks for long enough to realise that anyway.
He continues; "Time travel isn't a get out of jail free card. When you go rampaging through the past, it doesn't actually change the future. Everything that is happening now, happened before the time travel technique was even discovered in the first place. No matter what I do here, things are already set in stone to happen in that specific way."
Mitsuru closes her eyes, "An infinite loop."
"Sure, let's go with that. You both made it very clear to me that I needed to come here and give you this information. You've been preparing and researching how to do so for decades. In essence, the 'you' from the future is cheating, and giving you some of the answers now to set things into motion. From here, you'll both develop the technology and magic based on your own discoveries, and repeat the process all over again by sending another version of me into the past."
"That still doesn't answer why you need to be here," Mitsuru contests, "Are you saying that I couldn't discover the way to make my system work? If I couldn't do that – how did this future version of me get this thesis paper?"
Zandias grits his teeth; "That's the tricky part, we don't know. The real source of that information is a complete mystery. If this really is an infinite loop there's no way for us to find out. We can only guess that one copy of Mitsuru set this into motion by constructing the very first time machine."
"This might not even be my work," Mitsuru sulks.
"It has your fingerprints all over it, Mitsuru," he assures her. "Nobody understands interdimensional travel like you do."
He seems to know things that support his assertions of his real identity. But isn't this problematic? Why would he so willingly reveal the future to you like this? You pull him away from Mitsuru, "I don't assume you're going to tell me everything that's coming up in my life."
Zandias shakes his head, "Sorry. You told me to keep things simple for your past self. The only thing he wanted to say was that everything will work out in the end, you just need to keep doing what you're doing and trust your own judgement. I can tell you a few things though…"
"Like how I'm a devil?"
"Heh, pretty easy to figure that one out. You're one of the powerful, high-class devils in the underworld. Pretty obvious when you consider that you're married into one of the biggest clans around. I don't know how Mother convinced you to become a devil yourself though, maybe it provided an advantage in battle that was too much to ignore."
Him suggesting this to you may well be the reason that it even happens in the first place. You want to proclaim that you're above outside influence in making a heavy decision like that – but you're just a person like everyone else. It'll fester in the back of your mind for a long time, always there, waiting for the moment you crack and go ahead with it.
"And what a clan it is!" he laughs, "Some people call you a dirty geezer, but they don't know the family like I do."
"What's that supposed to mean?"
"You have a lot of wives, and a lot of kids to match. The Gremory clan went from a dozen or so devils to one of the biggest forces in underworld politics. It helps that a lot of my brothers and sisters are blessed with skills and abilities from other worlds."
Your face goes white at the implication. That is going to be a lot of work to manage. "Oh, I see."
Zandias finds your reaction amusing, but he moves to reassure you that it isn't so bad. "Don't worry too much about it. It's second nature to you in the future, and all of your wives are very supportive of you and each other."
"Chun-Li did tell me I'd have hundreds of them… I thought she was exaggerating." His face twitches slightly at the mention of her name. He's not very good at hiding his own feelings. Another question springs to mind; "So all of these wives are devils too?"
He wavers from side to side, "Eh. A lot of them. But some of them didn't 'need' the power of the evil pieces. Still, it's a big, tangled web of peerages with wives on top of wives on top of wives. I don't know how you even remember who's under who sometimes. I'll tell you something – a lot of traditionalists got themselves into a furore when they found out how many high-level devils you'd created."
"And there were people who were happy with that?"
"Ever since the triple war ended, a lot of devil leaders wondered why the clans were being so restrained with expanding their number. The underworld has more than enough space, and we were being left behind by the angels! Making sure that the big clans survive through reproduction is a practical concern for them. Some clan leaders took your example and had many children too, though there are concerns about internal conflicts over inheritance breaking out."
"You said you were the next in line?"
"Sure am. I'm the first-born son of the new Gremory line! Though, in actuality it'll take a very long time for me to be put into your position. Devils live for a very long time, and… hold up, I'm not gonna' say any more on that subject just yet. You'll have to wait a few decades and see for yourself."
You still have a hard time accepting that this is real. Who knows what kind of deceptive tactics the invaders are trying to use to get a leg up on you? He could be some kind of weird android designed to lead you down a darker path, or destroy you when you least expect it. You turn back to Mitsuru, who is again reading through the documents that her future self allegedly sent.
"So, do you think this is legit?"
She sighs, "I believe so. He's correct – this dissertation is exactly the kind of thing that I would write. I can't help but notice which details have been selectively removed as well. They're trying to prevent too much information from getting out. Anything that I create from beyond this point will be my work and my work alone."
Zandias smirks, "I could spill some personal details if you'd like…"
"No, we're good," you cut him off. "You can use that to complete the form change system?"
"Yes. I can," Mitsuru grunts, "As frustrating as it is to admit. I have been bested by my future self. These adjustments are minor, yet significant. I would not have been able to pinpoint them on my own."
"Don't think that it's going to be easy to finish it," Zandias responds, "You have a lot more work to do before it becomes usable. Not to mention designing the form change itself."
"And you're not going to give us any more hints."
"No. As I said, everything will work out in time. Victory is inevitable – you just need the confidence to go out and grab it."
You touch the bruise on your chest, "Easier said than done when Vali is running riot. Speaking of which, weren't you going to summon Asia?"
"Oh, right," Mitsuru says.
Zandias snaps back to reality, "I better make myself scarce then. Trying to keep this whole mess on the down low, can't do with letting Auntie see me."
"Auntie?"
He freezes up, "Ah, crap. Shouldn't have said that."
You don't know why that's such a problem. Obviously, Rias' peerage would have a close relationship with her children. You usher him away with a wave of your hand, "Alright McFly, get out of here before you do anything weird to the future."
He smiles, "Don't worry about a thing. You'll take a few beatings in this line of work. I better let Asia do her thing."
A magic circle appears under his feet and he sinks into the ground, disappearing from sight again. You have to wonder where he's staying during his trip to the past. A moment later Asia nearly falls on top of you as you lie back on the couch and try to avoid aggravating your injuries any further. You'd gotten so wrapped up in the time-travel shenanigans that you didn't notice how much you're hurting right now.
"What happened?!" Asia cries.
"Had a run in with the white dragon emperor. I'd really appreciate some help, Asia."
"O-Of course! You needn't ask!"
Asia summons her rings and begins to cast Twilight Healing on your body. It's going to take a while for you to heal properly, even with her assistance. Asia is visibly worried, "The white dragon emperor? How did he get here?"
Mitsuru is hopping mad, "I'll tell you how, those freaking invaders have been stealing my patented technology without paying royalties! I'm going to make them pay!"
"…If Vali is here, then not even the President would be capable of defeating him in battle. The only person who can stand up to him is-"
You finish her statement, "Issei."
"That's right."
"Say, Asia, you don't mind carrying a message across to him, do you?"
"Anything you want," Asia smiles. She really does have the face of an angel – an angel turned into a devil.