Lugnica

Ben Tennyson has not been a hero for over 2 years after the events of Ultimate Alien..

While he still possesses the new Ultimate Omnitrix that he and Azmuth constructed together, combining the aspects of the Ultimatrix with the New Omnitrix that he got after the defeat of Diagon, he no longer uses it due to severe PTSD that occurs whenever he transforms into an alien form. He is now merely a shut in college student that has retired from the hero life as the world falls apart around him.

That is, until he blinks, and finds himself standing in a completely different street..

In a completely different world.