Livin' in the Inaka

Wednesday after my last class got out I returned to the staff room at Seibu Elementary where I usually join the other teachers for afternoon 'otsukaresama' coffee and snack made personally by the school's lunch lady, often taken from her own backyard. This time however, I was approached by the head teacher who asked if I'd like to join them on a "short trip" into the mountains. She gave me a lengthy explanation of some annual excursion the staff go on to "nani-nani-natural-water-something-mountain-school-pool"... I like hiking, and they said it'd only take 30 minutes so I agreed "hai, ikimasu" to which they were all very excited about. Nakamura san then led me into an unknown room which I had previously assumed to be a closet, but was in fact a whole tatami room complete with closet, TV and a really nice western bathroom. She said it was her private changing room for when makes lunch (?). She hands me a really old, dirty shirt and pant