Ur a really great writer dude. Amazing ideas and adequate execution. I hope you go on to improve your art enough to gain a distinctive refined style that makes u one of the top writers on the internet. Everything is amazing, but something feels a bit lacking. Take this with a grain of salt, as its just some random lazy normie who can't gather up the determination to write his own fic is telling you, but I feel like ur story and characters are great, but the prose itself feels, idk why, lacking, like it can't keep up with the amazing story. Its like a webnovel typical writing style, which compared to your amazing story feels pretty shabby.
The more you use your chakra, the more it grows. Though there is an obviously limit for each person. Not everyone can reach kage level chakra. Akira own chakra reserves should be elite jonin or low kage level, for the story to make sense. But he can increase it in many ways. 1: Either use your canon knowledge, get into contact with Tsunade and gain her chakra storing ability, that would be a huge help. 2: Sage Mode. 3: After reaching a certain mastery of his ability, or after having tamed every shikigami (mahoraga included), it doesn’t cost Chakra any longer or way less. 4: Create a similar seal as the curse seal. 5: Seal a tailed beast into yourself. 6: Hashirama Cells. And that just came into my mind instantly. Many options
I'm wondering if the Ten Shadows domain will be implemented. The Chimera Shadow Garden used by Megumi was said to be an incomplete form, and existing information about that is quite lacking so I understand if you opt not to use it. But I still hope this can be implemented just to make the Ten Shadows complete. In the context of JJK, all cursed techniques come with an innate domain, and sorcerers use barrier techniques to release it but I have no idea how to implement it in Naruto. Maybe sage chakra, seals or something idk. But I don't expect it to be like a barrier domain but more like Sukuna's domain of actualizing in reality. Anyways whether you want to implement this and add you own thoughts or not the story is still very enjoyable.