The lost girl was a citizen in New Domino City, who got split up from her mother, when Aporia terrorized the city.
After Aporia broke the Turbo Duel circuit, he and Yusei Fudo dropped to the roads to continue their Duel. Yusei spotted the girl up ahead of them in the middle of the road, where she was kneeling down crying for her mother. Yusei halted his Duel Runner in front of her and told her to run away before Aporia caught up. Once the girl was safely away, Yusei drove on. Seeing the danger they were causing to the citizens, he decided to go to the old B.A.D. area to continue their Duel.