Wait

When Hua Youlin went upstairs, he found that the door of Gu Xiqiao's room was tightly shut. Even the light that usually escaped from between the door gap was nowhere to be seen.

The same could be said with Jiang Shuxuan's room, except for the fact that the lights in his study room are still on. 

"Big Brother Jiang." Hua Youlin rapped his knuckles on the door of the study room. The door did not pop open immediately but the boy knew that Jiang Shuxuan must've heard the knocks.

After a minute or so, the door finally opened up.

Jiang Shuxuan had changed into a new shirt. Looking down at the book Hua Youlin was holding, he stepped aside and allowed the boy to enter his room. "Is there another question you need help with?"

"..."

Hua Youlin remained silent. 

'Do I look that dim-witted?'

"Big Sis Gu has locked herself in her room all day long ever since she came home." Hua Youlin pursed his lips. "Her lights are off too."