Because you're an easy target, and you need to develope a sense of self-preservation. [he sticks his tongue out at Sora] What better way to get you to be more careful than by pulling pranks on you?

Hajime requested the lessons personally, how could I say no?

Oh. His name's Ekko, I don't know if you've met him. He tends to be up later in the day and well into the evening, and I don't think he gets out much.