Very nice work

Er... if Minato has been pulled from the Great Seal, then what is holding back Erebus and Nyx from pwning his old world?

what's going to be different with minato's persona power?

This opening feels standard but it creates a solid foundation for you to progress especially if you already have an end in mind. There will be quite a few changes so I hope you carry us through profound realizations instead of boorishly tossing out information like a summary. That sense of gravity and atmosphere is one of the keystones for a lot of these stories so I hope you remember that and seek to inspire similar yet unique feelings within the readers.

The best bits of fanfiction carve out new places in the setting instead of following along the source material. We've already watched the show. Rereading it with little bits added on is boring. DxD is a mythological free for all, so there's plenty of material to draw from.