Yu Qi returned to Binhai Nation with Long Hui. However, she did not return to FINN City first. They went to Capital City.
For what? To meet with Qin Xia. Since Yu Qi regained her memories as Qin Yue, she wanted to meet her senior brother.
Her senior brother had been alive all along. He must be very lonely.
Her senior brother probably knew her true identity. No wonder he treated her so well.
Long Hui also revealed something. Last time, they went drinking. She became drunk and met Qin Xia on that day.
In Long Hui's story, Yu Qi called Qin Xia, 'senior brother' and also called herself Qin Yue. At the time, Long Hui did not understand why Yu Qi called herself Qin Yue.
Then, the thing happened. Long Hui finally connected the dots and understood everything.
