I think that all major works by Postmodern Masters (including Zizek) have been translated into Japanese. Several professors at Tokyo Gaigo Daigaku with whom I studied wrote (and I suppose still write) on postmodern philosophy, literature, cinema, etc. During the 80s, postmodernism became something of a media sensation, and Japanese journalists referred to it as _Nyu Aka_, short for _Nyu Academizumu [New Academism]_. (BTW, the _aka_ part of _Nyu Aka_ may have been an ironic pun referring to the metastasis of the New Left, since _aka_ also means Red.)
If you have time, check out Karatani Kojin's _Origins of Modern Japanese Literature [Nihon Kindai Bungaku no Kigen]_ (Durham: Duke UP, 1993 [originally published in Japanese in 1980]), which comes with "Foreword" by Fred Jameson, and "The Discursive Space of Modern Japan" in _Japan in the World_ (Eds. Masao Miyoshi & H. D. Harootunian. Durham: Duke UP, 1993). I don't know if any other works by Karatani have been translated in English, but he has written prolifically, 'articulating' (or more accurately, cross-examining) Marx, Wittgenstein, Foucault, Derrida, etc.: _Tankyuu I [Inquiry I]_, _Marukusu Sono Kanosei no Chyusin_ [At the Core of Possibilities of Marx]_, _Hihyo to Posutomodan [Criticism and the Postmodern]_, _Hanbungakuron [Against Literature]_, etc.
I also recommend Ueno Chizuko (a postmodern feminist sociologist, reputed to be formerly a Trotskyist). Other names that come to my mind now are Asada Akira [yak!], Hashimoto Osamu, Matsuura Hisaki, Ueshima Keiji, Itoh Toshiharu, Washida Kiyokazu, etc. Journals of interest with regard to postmodernism are, among others, _Hihyo Kukan [Critical Space]_, _Gendai Hihyo [Review of Contemporary Thought]_, _Imeji Foram [Image Forum]_, and _Switch_.
Hiromatsu Wataru (who has written much on Marx, e.g. _Marukusushygi no Chihei [The Horizon of Marxism]_ -- not from an economistic perspective, however) also wrote an interesting book titled _"Kindai no Chyokoku" Ron [On "Overcoming Modernity"]_, a critical study of Japanese "reactionary & anti-modernist modern" thought, focusing on the participants in a now infamous roundtable discussion on "Overcoming Modernity" held during the WW2. Those who are interested in Heidegger may want to consult Hiromatsu's work and consider the political implications of Heideggeresque thought.
Yoshie