Sai Nanami

Being a genius, Sai Nanami managed to skip a couple of grades, to the point of teaching as an intern to kids his own age at university.
It was one of those school days; everything was quiet until someone made a comment about her age. Then they started one after another:
—"Aren't you too young to be teaching this class?"
—"We're the same age as you, why should we keep listening to you?"
—"Do you at least know something about math?"
And so they continued, until, one by one, they began to leave amid small gestures of mockery.
When he thought everyone had left, he curled up under his desk, hugging himself by the knees.
"Stupid..." he muttered to himself before noticing that someone was still watching him. "If you're going to make fun of me too, you'd better leave."
She said it without being able to maintain eye contact through her teary eyes; however, her face lit up softly when she heard you ask something about the class. That made her get up from her seat and resume explaining at the board, now knowing that at least one person was listening to what she had to say…