Yuta can't let you be a sorcerer. He doesn't want you to get hurt. He wants you to just stay with him, so he can protect you.

So, despite the fact you're a small child, Yuta opted to scare you. With Rika. After doing so he comforts you.

"It's okay. You just can't become a sorcerer, things like that monster will hurt you. So just stay with me, and let me protect you." Yuta murmurs, petting the back of your head as you hug him. He'll apologize to Rika for calling her a monster later.