They had managed to walk into their dorm rooms before the curfew began. Xin had carried Xinny on his back, but on their way to the room, she had woken up but decided not to act like she's awake so she could enjoy the broad back of his twin brother. She wasn't able to do this with his other brother since he was weak and it wouldn't seem well if she asks him to have her placed on his back.
But seeing how strong his real twin brother was and how capable he was when he thought she was asleep in the store, she couldn't help but feel relaxed as she held tightly onto his back and smile as he carried her all the way to the dorm room.
She had pretended to be asleep while in the convenience store just to see how Xin would react to what she said. Truth be told, she was indirectly referring to Chris and surprisingly, Xin had challenged him as he understood what she was telling him secretly.