I think that the women being unable to have kids without aging, is as some might have said, is a cop out that is beneath you. Personally I would have made it so that each woman can give birth X amount of times and their children would have similar longevity to Hagamoro's, as in a few 1,000 years as well as being able to fall in battle, relinquish their long lifespans, while maybe opening up the other planets as possibilities for frontiers in the case of overpopulation, then there's the option of the other connected dimensions, like what Kaguya and Hagamoro can access. Also the cost of creating new life in my mind would be a dramatic drop in chakra levels until the child is born, maybe even weaned, and then the chakra levels steadily return to the prior point. Also I think it's a decent idea to have the lifespan of their descendants decrease with every generation until it is around 115 years of clean living. Also I have to ask "Why so many Bleach characters?" Honestly between the large number of Bleach chicks and the whole have to give up being virtually immortal to have a child, and for some reason it can't be Naruto as the father, due to overpopulation as an excuse is kinda killing how much I love the story. Now I am aware that the story is still going on, so it would mean so much to me if you considered my review and alternative options to the having a child bomb you dropped in this chapter. If you don't like my ideas or a just WAY too far along with the story to make such a change in any of the zero-Ninja stories feel free to say so. Also their is SO MUCH more to having a child then ensuring that you continue to live on, it is a journey that can make the world seem like a better place, and I believe that the inability to have a child with out giving up a change that was made to me, for example,would be more than a bit of a deal breaker for me. I also think that the sterility thing screams a bit too Twilight and Dark Hunter series. After all I often read of Naruto wanting to have a family as well as becoming Hokage as his dreams. Although I suppose it could be me being my usual hopeless romantic, that wants to read about Naruto and his loves raising children in a time that peace has begun to reign.
Also I think that the Final Fantasy/Taki-Trio should have standing orders to obey Naruto on the same level as Kimioko.
Author's response
To be honest, to my way of thinking, your arguments about kids are born entirely of your desire for them to appear in the story. Not of anything actually found in the story itself. I can't be held to those expectations, or what other authors do to meet them.
Now as to why kids will not be appearing in this story. Well first off, it really didn't do the canon Naruto any good now did it. I mean the Naruto that you described doesn't even exist in Kishimoto's version considering how his son resents him. If anything, I'm almost grateful canon became such garbage since it just further validates my reasons. I mean if Naruto in canon can't manage to be Hokage and a good father. Then how do you expect my Naruto to balance what he needs to do, with the numerous relationships that he has. A child requires far more attention then an adult. Mix in his possibly having dozen or more at a time then what are the odds some of them feel ignored without the understanding that an adult would have.
Furthermore, I don't believe you are really looking at things from Kiyomi's point of view. In Eroninja, she is many hundred of thousand years old. She watched humans go from small scattered tribes to covering the entire continent. She is taking a long view because the end results would be unsustainable.
All the solutions you provided truthfully to me are just about satisfying your desire to see them appear. I mean why give any of them irregular lifespans, is it because as more time goes on we'd care about the next generations less and less so they can just die. Kind of sounds like out of sight out of mind to me. I know that isn't how you intend it, but that is how it looks to me. It is kind of like how most governments run huge deficits as they borrow money to pay for promises they made today. But are being paid for by the next generation and the one after that, until one of them is the one left with a debt that cannot be paid because there is no one left to borrow from.
Isn't the responsible thing to do if you know an action has bad consequences down the road is to not engage in them. That is why they have a choice potential live forever and remove yourself from the natural order of reproducing or have a kid and return to it.
Finally, there is also my version of Naruto to consider who doesn't want kids. I mean if he has to choose between children and a life of blissful self indulgence with a harem of women without them. I imagine he is quite eager to be signed up for the latter.
PS. Heck, the kids helped ruin the Naruto manga and that to me tends to be the trend. For every good child that appears in media like the Six Sense, there are dozens like the live action Avatar: TLAB movie or the brats that appeared in the Lost Word.
PSS, the reason so many Bleach and other characters appear is because there are only a handful of kunoichi in Naruto, and considering the number needed for a place like Konoha that would be inclined to role with what he wants. Wouldn't just as many be needed in other places. As such I either needed to create OC's, or pull from other media. I choose the latter.