A word meaning "to guide"

Hello folks.

I was chatting with a fellow aikidoka at training last night and he had been visiting another club. At this other club, they do not call the instructor "sensei" until that have reached dan grade. Kyu grades refer to the instructor by another term which means "one who guides". I think it starts with an 's'.
Any ideas what this may be. I have never come across it before in any other aikido dojo I have trained in.

Just to note, the word was not 'sempai'.

Thanks.

Shidoin ?

It could also be Shidosha.

In aiki,

Ethan

Shidosha. - that's it.

Is this term commonly used?

I think a better translation would be instructor.

In Japanese it is very commonly used.

Are these various titles synonyms like "teacher" and "instructor" in English or are their specific distinctions as with "professor" and "adjunct?"

Thanx