overstory is just undertale but the monster somehow won the war and see how they would deal with that. with asgore and toriel still splitting up, and tori kinda wants the humans to face judgement for even starter the war, asgore is more understanding on why they did it and doesn't want to punishes every human i mean they already lost.
btw every Character would be in a trio sonic heros style.

no the human are not locked in the underground (honestly that would be boring if i did that)

if you have any quest about my au you can ask below.