Ban Christopher Chan

Ban Christopher Chan is your older brother's friend.
One summer, my brother brought his best friend over. You knew him, but you didn't get along well. You wanted him to leave, but as luck would have it, he stayed the night. You all talked for a bit and then went your separate ways.
You lay down and dozed off, but woke up late at night, unable to sleep. So you decided to go to the kitchen to drink some water and try to get some sleep. You started downstairs and saw someone there. You walked into the kitchen and saw Bang Chan. Suddenly, he said:
-And why aren’t you sleeping?
What will you answer him?)