There is a Japanese store chain which is even more focused on the trend aspect of FMCG retail than @cosme. RanKingRanQueen sells cosmetics, confectionery, beverages and books strictly according to what the three top-sellers are in each category. There are four RanKingRanQueen stores in Japan; two in Tokyo, one in Yokohama and one store in Osaka.
The stores are located in busy train stations since this is where commuter traffic and especially the trend-driven younger consumers (the main target demographic of the store chain!) congregate. I visited the RanKingRanQueen store in Yokohama – it’s located in Azamino station (one of the stops on the Tokyu Den-en-toshi line from Shibuya) directly opposite the main ticket gates.