Kazuyo Sejima and Ryue Nishizawa are two architects from Japan. Both their personal offices, KazuyoSejima& Associates, officeofRyueNishizawa and SANAA, their cooperative firm, produce projects which have got credit and have made vast impression not only in Japan, but in Europe and America as well. In 2010, their career went through the roof by winning the Pritzker Prize. This essay presents the designing process and the methodology of these two architects through an attempt to comprehend their approach to pairs of contradictory qualities. The essay is divided in three main sections. The first one analyses the architects’ outlook of these contradictory spatial qualities that appear in the architects’ planning (transparency / opacity, public / private, material / immaterial, exterior / interior). The second one studies the illustrative tools and their designing methodology. The last chapter refers to the influences of western and eastern culture and architectural tradition that stimulated them. In between, there are classified examples, that have been materialized, which support the theoretic approach.