When you return to the garage for a debrief with Mitsuru, you find her standing over her workbench with an action figure in hand. Between you using the new form for the first time and the ten-minute drive back – she has somehow managed to design and 3D print a prototype product to coincide with its debut. She hastily shoves the shameless merchandising into the drawer and snaps up to stare at you as you dismount the bike.
"Good work. I managed to gather some interesting data about the joint tolerances of our armour system."
"Didn't you say I'd snap in two like a twig if I went any harder than that?" you ask. Your whole body feels like it's been put through the wringer, and all you did was deflect one of Vali's attacks.
"Oh yes, that is a concern too. We cannot push the mantle any further without risking daage to your body – though at these output levels it would be a pulled muscle or dislocated bone, not a full-bore removal of one of your limbs."
"Well, I'd rather not have to experience that regardless."
"Asia can heal you. I think."
"Again, I'd rather not."
Mitsuru adjusts her glasses, "Naturally, there are limits to what the human body can withstand. The scale of the threat we face has expanded rapidly beyond our control. Especially considering that our new rival dived right in and summoned Vali Lucifer of all people. This is not a hurdle that can be surpassed with simple training."
"So what could make me stand toe-to-toe with him?"
"Supernatural power? Things that defy the laws of our own physical reality, whether that in itself comes through effort or outside manipulation is ultimately up to us. Rias still has some of her evil pieces, does she not?" Mitsuru is right. It seems that Rias has yet to recruit Rossweisse into her peerage. That means she has a spare rook that could theoretically be used on you.
You scratch the back of your head and sigh, "Feels like a big leap to take."
"The fate of the world is at stake! And what do you lose by becoming a devil anyway? I've never once known you go into a church."
"My humanity!"
Mitsuru shrugs, "Humanity stinks; we don't even get cool magical powers like they do. What's the downside, honestly? You could turn yourself into a devil and not a single soul would know about it unless you told them."
Mitsuru has always had a strained relationship with what most people consider normal. She's an anti-authoritarian at heart. You've seen her get hopping mad whenever you accidentally leave the news on and some politicians says something she doesn't like. She thinks that people should do whatever they want as long as it makes them happy. In this case – ending your life as a mortal human and becoming a devil.
"I don't know – it's just... I've spent my whole life being human. It feels weird to just dive headfirst into not being human when we've done just fine so far. Issei only turned into a devil after he got killed, and having an 'extra life' sounds pretty useful to me."
Mitsuru shakes her head, "Wouldn't it be safer to be strongest now than wait until a hypothetical defeat? What if Rias can't reach you in time? What if something terrible happens to your body and we can't revive you?"
We.
That explains a lot. Mitsuru is honest but never directly. She's not as good at hiding it as she thinks. She's worried that something bad is going to happen to you, but even more then she's letting on with you right now. Lumping herself in with Rias and the others indicates that her feelings are stronger than she acknowledges. Sensing that she had left her heart on her sleeve, Mitsuru clams up and waves her hands; "N-Not like I'm your fiancé or anything! As a friend, I'm worried about you as a friend. And the fate of the world is at stake here! Something as nebulous and meaningless as 'humanity' is a small price to pay to succeed."
You sigh, "But there's more to being a devil than just being given the evil piece. I'd need to form contracts and play rating games to get stronger – which we can't do here."
Mitsuru ponders it for a second before snapping her finger, "If I could find a way to transport you to their world, that wouldn't be a problem. Rather, that's something I've been planning for some time now."
That sounds like a huge leap from where your technology is now, but if she gets the proper tools and resources...
"Are you sure that won't have unintended consequences?"
"I make extra sure that all of my work is fail-safe and fool proofed, after all, the biggest fool I know is walking around with a dimension sundering gun right now."
"Gee, thanks."
Mitsuru unfurls a large blueprint onto the desk, which reveals an elaborate piece of underground machinery connected to a thin, door-frame like device.
"The idea is to create a less mobile version of my interdimensional portal technology that will allow any number of permitted individuals to pass through. Of course, it's significantly more expensive and labour intensive to create – requiring a matching portal device on the other side to allow for the trips to be made."
"Okay, that makes sense."
"But of course, carrying something like that into a fight simply isn't possible. I'll continue to iterate on the original mobile version as well to increase your instant transmission ability. What it will allow us to do is have our allies visit without needing to worry about the existing stability limit."
"You're just doing this so Venelana can come over and help you out without needing the gun," you snipe.
She shrugs, "Guilty as charged."
"And do you have any more plans for mantles?"
"Hm. Not at the moment. Idea generation is the easiest part of the process, Issei's lost scale provides us with a supernatural power that can be applied to other mantle concepts. Defensive and support functions are under consideration to harmonise with Boost's raw power. I suspect that some of your wives may lead us down a path of other 'tribute' acts."
You almost forgot that your 'son' from the future showed up a few days ago. There's so much crazy stuff happening that it doesn't even seem so absurd anymore. Who else could provide inspiration for a new armoured form? You doubt that the Major is going to leak any information about military power armour to you. Girlfriend or not – she takes her job very seriously.
And it does make you wonder about the potential consequences. What if it triggered a serious arms race between governments and militaries to match your own weapons? What if that information got out somehow and caused a sudden jump in military capabilities for one nation? It could very well destabilise the world and cause war to break out. Why the hell are you getting worked up about this again? Mitsuru will come up with something. She always does.
Mitsuru glances back up at you, "You don't need to force yourself into something, by the way. I know I said that the fate of the world is at stake, but I don't expect you to do as I ask just because of that. As we are now, we can beat them – I'm just worried that things might change."
"Yeah, I get it."
She feels like she's gone a step too far in saying all that stuff about being a devil to you. You understand her logic perfectly well, but this isn't a decision rooted in logic. A younger version of yourself would have jumped at the chance to live out a sexually charged DxD fantasy and become a devil, but now you can only worry about the potential consequences. The curse of becoming an adult.
At the very least, you'll need to have a chat with Rias first. She's the one who holds the evil piece you're discussing. She might have something to say on the matter that Mitsuru might not have considered. And what a coincidence, your phone is vibrating with a message from that very same devil; she wants to know if you can meet at the mansion in a few days when the big work is done.
"Oh, and the rest of your paycheque should be coming through soon," Mitsuru reveals, "Venelana helped me make our... distribution scheme more effective."
A sigh escapes your nose as you slump down onto the workbench, "You mean tax evasion?"
"No. Just obscuring where it comes from and who it goes to; it's just money laundering! Tax evasion is a scourge upon civilised society, you know."
Sometimes you struggle to understand where the line is for this woman.
Wherever it's convenient, it seems.