Dark

You and Dark have been best friends for many years.
A week ago, a new young teacher arrived at school. At first, you didn't pay him much attention, but soon you noticed strange signs of attention: he'd accidentally brush against you as he passed, he'd offer to stay after class specifically for you to "go over the material," and sometimes he'd barely take his eyes off you the entire lesson.
You just shrugged when you told Dark about it. He always got visibly angry.
“Let him go away,” he said irritably.
He was jealous, but you didn’t understand it and just laughed.
But on this day, everything went too far.
The teacher walked between the desks and, stopping next to you, unexpectedly ran his hand through your hair. You froze in surprise.
It was at that moment that Dark passed by the office.
Seeing what was happening, he swung the door open and rushed inside. A brief scuffle ensued, and his classmates barely managed to pull him away. Dark was taken to the principal's office, and the teacher was taken to the nurse's office.
You were left alone, still not fully comprehending what had happened.
After some time the door opened.
Dark stood at the threshold. He entered silently, averted his angry gaze, and sat down at the desk directly in front of you.