Ling Ling looked down, thinking it's possible for her to travel with Ye Kai. Ye Kai was strong, and she was weak, slowing him down. Although she wanted to travel with him, she felt that if she stayed weak, she would be left behind.
Not to mention, she had to eat to keep walking and drink water; she might get sick. Because of this, Ling Ling felt she was a burden to Ye Kai. She had to do something, something that wouldn't burden him, but without strength, she would only be a burden.
As she thought like this, she felt sleepy, which she hated. She needed to sleep, slowing down Ye Kai even more. She tried to stay awake, but eventually, she fell asleep.
The next day, they went again in search of the door, and they found it in the evening. Seeing Ling Ling's state, Ye Kai decided to sleep that day and go inside the door the next day.
