Emperor and the Imperial family. In particular, a "chrysanthemum crest" (菊花紋章, kikukamonshō or kikkamonshō), i.e. a mon of chrysanthemum blossom design...

called the Chrysanthemum Seal (菊紋, kikumon), Chrysanthemum Flower Seal (菊花紋, 菊花紋章, kikukamon, kikukamonshō) or Imperial chrysanthemum emblem (菊の御紋, kikunogomon)...