[Naruto][RFC] Considering Writing A Sequel To An Old Fanfic And Need Some Advice...

[Sirrocco]

Possibly *let* it be somewhat separated in time.  Write a prelude where Tsunade gives a briefing to some random side character (deliberately/explicitly not identified at the time) who wasn't otherwise involved, as part of giving him/her a long-term assignment that involves them doing stuff quietly for a while.  At some point after the story kicks into full gear, this character shows up again, having just finished a year's worth of plot-relevant prep work.  Let you get in your exposition and set up a heck of a Chekov's gunman at the same time.