what is the name of the ruling dynasty in japan
Perhaps you mean what dynasty reigns in Japan. Akihito is the reigning Emperor of Japan, the 125th emperor of his line according to Japan's traditional order of succession. He acceded to the Chrysanthemum Throne in 1989. If you read wikipedia, you will observe a more balanced view of China's dynasty. Currently, and namely, there are 2 dynasties in China, with PRC being the de-facto ruling dynasty, with another less powerful ROC dynasty.