User blog comment:Crimson and Darkness/Shin DxD 3 discussion/@comment-9307023-20190811022813/@comment-1359322-20190812010152

Except Ishibumi already said the Kyuubi is essential to Kyoto. Without Kyuubi, Kyoto would be doomed because the Kyuubi is the being controlling the flow of Ki in Kyoto. Hence why Kunou can't join not because she's a princess but because of her importance to her city.

If Ishibumi does that its not just a change in decision, he's literally going against his own plot.

"“The flow of ki in all the regions of Kyoto is still stable. The nine-tailed fox is an existence responsible for maintaining the balance of ki flowing from the different areas of this land. Kyoto itself can be considered a large-scale force field. If the Kyuubi had left this land or had been killed, then Kyoto would have undergone dramatic changes. Since there are no signs of that, it means Yasaka-hime is still fine, and that the kidnappers are likely still around.”"

- Volume 9