Dieter Haffner

If my teacher would ask a 5th kuy to lead class, I would be glad for her to get the opportunity and support her in every way I can.
It would be interesting to see how he sees and thinks about certain techniques.
In fact, I am planning to let the students teach a technique they favor the next time I substitude (if the teacher agrees with it). Don't tell them yet, it needs to stay a surprise.

But to have a 5th kuy fall in, every time the instuctor can't make it, and when higher ranked people are present, is a bad idea IMHO.
The aikido initiator course (teaching children and beginners up to 4th kuy), regulated by the governement, requires at least 1st kuy. So you might say that a 5th kuy does not have enough luggage yet to be teaching it peers.

Now you might say:
- "But the 5th kuy is a very talented student that might turn out to be a great teacher one day.". Sure, but the instuctor should be present for support and adjustments when needed. But don't leave him alone in class.
- "But that 5th kuy is a 3rd dan in this other art". Sure, but tell him to teach some stuff of his own art (maybe something he thinks relates to aikido).
- "But teacher said so". Sure, but ask yourself (as a higher rank) what the reason that the teacher picks this lower rank over you. Then try to do something about it, not for yourself or your ego, but for the club.

When a 5th kuy is the first substitute for a class (when higher ranked students are present), there is/could be something wrong with the class/dojo.
Maybe the class hours fall really bad so that it is hard to be in class every time. Maybe some rescheduling is in place?
Maybe the 5th kuy is the best aikidoist/teacher the instructor has. But then the instructor should start to think why all these other students are not good enough.
Maybe the 5th kuy is the only person that is commited enough. If the sempai's can't catch the clue, the instructor should have a talk with them.

I do not pick on lower ranks (we all were lower ranks and still are lower ranks to many), but if you need to rely on the lower ranks, it might be time to think a few things over about your dojo.
Because after all ... Another thought:
Although "Shut up and train!" is a good answer.
Sometimes, as a sempai, you need to "Speak up and train even harder!". And not for your ego, but for the best of the club and trainer.

I hope this clarifies my previous post.