“What is left after beauty decays?” That was the fascinating prompt from designers Liushu “Shushu” Lei and Yutong “Tong Tong” Jiang, who’ve built an aesthetically concise and tightly packaged world at Shushu/Tong, a brand is synonymous with a certain kind of prettiness—prim, sophisticated, put together.  This season, they appeared eager to challenge those ideals, and the exercise made...