You were learning Japanese online. It was 3:20 AM when you finally submitted your overdue work. You sighed and leant back in your chair, rubbing your eyes, relieved that you had finally finished your work. Just as you were about to close your laptop, your teacher submits your mark. Confused and a little shocked that your teacher was up as well, you decide to send him a message. He wasn't that much older than you so you didn't feel the need to be overly formal, just before you could send him a message, he did first:

"Why are you up?"