From a technical(grammar) standpoint the story is still good. Plot-wise I'm unsure and need to see more. Right now it seems there was no reason for the first twenty chapters if Shun's existence effected nothing. Thanks for your work author and keep going.

I would hope the character would go to a different future Konoha. If not then changing the past would be pointless. What would be the reason for the past chapters otherwise. Seeing a Konoha filled with Uzumaki and others because of the butterflies Shun caused. Maybe some main cast would be the same. Whatever you decide as long as it is minimally interesting I'll read it.