When you watch anime, you open yourself up to a culture that’s very different from the West, and it’s not uncommon to encounter an idea or two that can be hard to understand, even if you have subtitles to read. Concepts like senpai (an upperclassman in a school or senior in an organization) and kohai (the opposite) were strange to me, as were “cram schools” where students memorized information to be regurgitated on a college entrance exam a few years hence. Another concept that took me a while to figure out was gasshuku (translatable as “training camp”), essentially when members of a club or sports team spend several nights at a separate location so they can practice their sport or activity for hours on end without interruption, as everyone in the group polishes their kiai (“fighting spirit”) and generally get energized to do well. It’s yet another concrete example of Japan being a very group-oriented place, and an interesting lesson in Japanese culture for us, on the outside looking in.
Training camp side-stories are common in anime, and K-On! manages to have two of them.