In Naginata, you can take many roles. Some roles only apply during practice (like sensei for teacher), while other roles also apply outside practice. You can, for example, have the role of a senpai or kohai. These two roles represent a hierarchical relationship, in which the senpai (senior) has more experience and a higher level in Naginata than the kohai (junior). The picture below represents this relationship.
The senpai has a higher position that the kohai, but he or she should assist the kohai as much as possible in Naginata. This relationship also explains, for example, when you do a line up just before and after practice, the kohai sit away from the shomen while the senpai sit near the shomen. (The shomen is a sacred and safe place and therefore a better spot.