I somehow feel as though the only reason Mittelt didn't get killed was because of pairings, which I feel kinda cheapens both her survival and Kalawarner, Dohnaseek, and Raynare's deaths.

I dropped my cat from less than a foot off the ground before. he landed on his back

I swear the ages are all fucked?
Apparently he's the same age as Koneko, who should be younger than Rias, despite the fact that Rias hasn't been born yet?
Oh, and then you've fit the fact that apparently Kuroka and Shirone are still together? This is way different from Canon.

Ahh yes. Kuroka like most cats has a habit of sleeping on limbs and making their owners uncomfortable.

Im not super onboard with idea of changing characters ages.

Really ... Wow. I'm sorry, but this minor plot-twist/hardcore nerd sucks. The temptations to drop and move on have gone 0-100 here. So we have MC who seems to ignore everything he has (would have) learned for plot reasons, then on top of it the near life/death experience basically cripppes him (would have been better to maybe weaken him momentarily but strengthen his foundation), then a bunch of sappy "I'm not a useless side character I will save you for love!" moments on top of all that ... feels like the reading equivalent of eating a brownie that turns out to be mud (not as bad as $hit, but getting there). Fingers crossed this does a 180.

Unfortunately, I am going to have to drop this story at this chapter. I have several reasons for this:

1) Simply this story is too slow. I believe as a writer you should have a general idea of where you are going in a story and advance it at a decent pace, but you have become too bogged down in details. Honestly, by the end I was skimming if not skipping chapters and still able to easily keep up. Not something you want a reader to do. I even skipped ahead to the final chapter and at 573,000 words you are still only when he is like 14/15.

2) I have always found that things in this story make no sense in regards to the DxD universe. Granted, ff is about creating new stories or changing the world a bit so I let a bunch go, but there are some glaring issues. Caine not using devil magic to teleport or use it in communications. Caine not sending a message to at least let Ravel, Sirzechs know that he is alive and ok. The fact that such a city of Kaili even exists along with what seems to be an infinite amount of stray devils.

3) I don't much like Caine's personality as it has stretched on. (Also the sex at 11/12 thing is a kinda... besides he had barely entered puberty and it was probably the size of a pinky.) Also, and this is more personal, I really dislike the fact that he has basically slept around behind Ravel's back. She deserves so much better and I hope she breaks the engagement and doesn't end up with him. That would be poetic justice.

All that said I do have a couple positive takeaways from this story.

1) I do like how you made the DxD universe a more cutthroat one with a lot of bad shit happening. This is way more realistic and I would have liked to have seen how Issei would have faired.

2) You write well. Good grammar along with chapters not having overly long paragraphs of dense information, which is ironic considering I said that it moves slow.

Best of luck in your future stories. I do believe if you moved a story at a faster pace with characters more related to the heart of the series with a neat idea you could do well.

yo...were the hell are all these stray devils coming from

You know what would really be deserving? If Ravel finds herself someone else

Yeah... Caine is an absolute hypocrite. At least he semi-recognizes it. Still, allowing human trafficking to occur for your family to protect from greater "evils" and then get mad about a devil making a Nekomata go too far in Senjutsu is well... obviously he just dislikes that it hurt Kuroka and Shirone.

Now, Ik Caine himself is innocent of those crimes his family committed, but he should recognize his parents weren't better at all as High Class devils. I mean seriously, human trafficking...

Okay I like the story so far, but my main question is this:

Why does Caine not teleport to Gremory or Phenex territory or use a communication spell to Ravel, Sirzechs, etc? It seems this is really basic magic that anyone can do in the DxD universe.

Gotdamn. The character arcs in this make shounen seem like kiddy pool stuff.
Vallia starting off as frightened and timid, with practically zero confidence before trial and tragedy turn her into a force to be reckoned with, confidant and bold.
Caine as a somewhat lost and 'reluctant to lead' persona that relies on others to call the shots turning into a decisive and terrifying powerhouse.
There's almost no inconsistent or bad characters to be found but those two always stick out to me, and the utter Hell they gonna raise back on Devil land.
And they fuck like you wouldn't believe.

Now that really sucks. No one of any REAL plot importance died, but at the same time it sucks infinitely more because they failed to accomplish their objective, and now Caine has to snap Vallia out of it.

Honestly, I can't even be happy that some of my predictions were right.

Just kinda feel empty - which is probably what you were going for. Kudos on that at the least.

I don't know man, I kinda wanna see Caine die.

He's already probably fucked up canon, so if he kicks the bucket in a spectacular way that'd be pretty cool.

Other then that, my predictions are. David's dead, Lisa's dead, 2 fallen angels (at minimum) are dead. Chows dead, and if you're feeling ballsy Kurokas dead. Maybe Caine whips out "full strength" senjutsu?