My mother-in-law, Nanako-san, who had moved to Hokkaido with my father after his job transfer, came back this summer to check on me. She is as beautiful as ever, and being in the middle of puberty, I still can't bring myself to treat her like a mother. One afternoon during a severe heatwave, I saw Nanako-san hanging laundry on the balcony. The sweat trickling down her neck, the sweat pouring from her armpits, and her blouse soaked through with perspiration... Seeing her body drenched in such erotic sweat, I felt an uncontrollable desire, and before I knew it, I began to see Nanako-san not as a mother, but as a woman...