Re: how to deal with my sempai
as a shodan i have recently been given chances to lead classes here and there, and i find it exceptionally rewarding.
I too find myself in similar positions sometimes.
i think it is clear that this feeling is caused by the unspoken but present etiquette regarding rank, clashing with the reality of differences in skill and ability.
i think the best thing is disclosure, a casual disclosre that, as a communicative act, can free you from those 'unspoken' contradictions.
Next time your leading and that person is there, call him up to take ukemi and tell the class something like "Mr/Mrs. X here is better at this then me....let's see how this works when i do it against someone with his/her ukemi skills"
"Mr/Mrs X, onegaishimasu....class, ill take ukemi here...watch how X executes this...."
In either case, i think addressing the difference in skill is useful as a) a teachable moment b) a chance to show the class that skill does not have to coincide with rank, and c) a chance to work on your own ego, and show the class that you are humble enough to accept the skill difference between you, and not let it stop you from sharing your own level of knowledge with everyone.