Pure
If it's made of thread, your barracks will be pure. If you build it out of clay or bricks or wood, it will inevitably have some dirt in it. Build it out of thread to keep it pure of... well, impurities.
じゅん
None
None
Unfortunately, this pure thread barracks can only be used in June (じゅん). Any other time of year there will be snow and rain and mud that will get tracked into the pure barracks and ruin them. But June is the cleanest, most pure month, so you can use it then.
An update is needed before you can continue but you have more than one WaniKani tab open.
Finish up what ever you are doing on the other tab(s), then close them to continue.
The update will complete automatically once the other tab(s) are closed.