Re: How to deal with my sempai?
I recall one dojo I trained in where the instructor assigned us teaching when he was out of town. There was a sandan in the area of a different background. Our instructor made sure we knew that it was our class and the sandan was not to teach even though we were first kyu. He made the teaching decision. I also saw him throw a rokudan visiting from Japan off the mat who was being abusive to students and he was only a sandan. In fact, he was told in a very direct manner he was not welcome back.
Teaching ability does not necessarily correlate with rank. I have yudansha that I won't let teach despite wanting to do so badly. When they can communicate what I want them to communicate that situation might change. I chose who I want to recognize to teach, not the student.