In the Japanese martial arts, the understanding of junior and senior in the dojo- sempai and kohai is important.
Junior and senior in this case does not refer to age, but rather experience in the art or the dojo.
Simplified, those who started before you in the art are your senior, and those that started after you are junior.
Each junior and senior has a place to contribute in a dojo setting to help promote harmony and keep things running.
The smoother and better the dojo runs, the more time that can be spent training- the more time that the teacher can share lessons.
Sempai and kohai is about reasonability and the optimization of time.
Having explored the sempai relationship, what about the kohai or junior?
The best way to be a good kohai is to watch the sempai in the dojo and do what they do.
How do they bow in?
How do they help with setting up the dojo?
How they conduct themselves in terms of rules and etiquette?
In doing this, when a question arises regarding what to do- as them.
You can ask a sempai in the dojo anything, it is part of the reasonability regarding harmony that the sempai have to the kohai.