横浜美術館
Oiwa's work is held in public collections including The National Museum of Modern Art, Tokyo (Tokyo), Museum of Contemporary Art Tokyo (Tokyo), Mori Art Museum (Tokyo), Yokohama Museum of Art (Kanagawa), Toyota Municipal Museum(Aichi), Hiroshima City Museum of Contemporary Art(Hiroshima), Hyogo Prefectural Museum of Art(Hyogo), 21st Century Museum of Contemporary Art, Kanazawa(Ishikawa), Utsunomiya Museum of Art (Tochigi), Phoenix Museum of Art(Arizona), Arizona State University Art Museum (Arizona), Prince Albert II of Monaco Foundation and University of São Paulo Museum of Contemporary Art (USP).