What exactly happened to Satoru Gojo after being sealed in the Prison Realm? He didn't expect to be thrown back in time, yet alone another universe! Gojo found himself in the Underground. Imagine his surprise when he runs into his girlfriend from his present timeline, Lucy Ackerman, along with her older brother, Levi. [AU from Lucy Ackerman.] [Please read Lucy Ackerman first to understand this story.] [JJK x AoT Crossover.] [Disclaimer: I only own Lucy Ackerman and her plot.]