Thank you to Sensei Hoffman for providing the subject and content for this blog post.
More than simple seniority, senpai implies a relationship with reciprocal obligations, somewhat similar to a mentoring relationship. A kōhai is expected to respect and obey their senpai, and the senpai in turn must guide, protect, and teach their kōhai as best they can. Senpai/kōhai relationships generally last for as long as the two people concerned stay in contact, even if the original context in which the senpai was senior is no longer relevant.
Two people may both be students at the same school, but if one is a first-year student and the other is a third-year, then that would constitute a senpai/kōhai relationship. I feel the obligation is more important for the senpai than the kōhai in that it should be their responsibility to teach proper etiquette, traditions, rules of the dojo as well as mentor their progress form a technical standpoint.
A common misconception is that the senpai acts the same way a sensei (先生), or teacher does. There are some similarities between a senpai and sensei, but there’s also a big difference between the two. It’s rare that a senpai ever becomes a proper teacher to his/her kōhai although they usually remain in the same sort of senpai/kōhai relationship.
I think we all should study this concept along with our training to both learn more about it’s importance within the dojo, and understanding of the karate we wish to comprehend.