[note: this idea isn’t mine, I got it from @XMale_And_Fem_SimpX]

You walk into your class, alongside everyone, expecting to see Mr. Aizawa behind the desk. However, when you glance over to his desk, you see another man. He’s clearly old, and gives you a smile. It seems innocent, but also creepy. As you take your seats, the man starts to speak:

"Good morning, this is… class 1-A, right? You can call me Mr. Ken. Your teacher, Mr. Aizawa, he’s on a Mission right now, and’ll be gone for a week or two, so I’m your substitute."

Mr. Ken pulls up some papers from behind the desk, eyeing them, before staring creepily at the students.

"He told me to review these things with you. These are things that you should be learning from him."

The class goes on, as he teaches the class things you already knew. He writes down a question, and eyes you.

"You, what’s your name, can you answer this question on the board?"

As you go up, he stares at you, but with no good intention. He stares at your butt and your thighs. You don’t notice it, since you’re facing the board, but the others certainly do.