After two years, as a lecturer at the Institute of Japanese Studies, Kreiner habilitated in Japanology in Vienna, under Alexander Slawik.
[2] Kreiner is a pioneer of ethnological Japanese research and a specialist for Okinawa and the Ainu.
He was the first director of the German Institute for Japanese Studies and was later founder of the Philipp-Franz von Siebold Foundation.
[3] It was named in honour of Philipp Franz von Siebold, German physician, botanist, who achieved prominence by his studies of Japanese flora and fauna and the introduction of Western medicine in Japan.
In 2013, well after his retirement, Kreiner worked as a visiting Fellow for special tasks at the Hōsei University to supervise, among others, the newly founded International Association of Ryukyuan and Okinawan Studies.