In the first year of Tianbao (742), Japanese monks Rong Rui and Zhao Pu were entrusted by the Japanese Buddhist community and government to invite him to give lectures in Japan, and Jian Zhen readily agreed. From that year to the seventh year of Tianbao, 12 years, he led the people to make five expeditions to the east, but they all failed because of the sea waves, rocks, shipwrecks, sacrifices and the obstruction of some local officials. Especially for the fifth time, it was attacked by bad winds and wild waves, and drifted at sea for 14 days, and finally drifted to Zhou Zhen (now Ya 'an County) in Hainan Island. On the way back to Duanzhou, Japanese disciple Rong Rui died and Jian Zhen mourned. Coupled with the hot weather, he suddenly suffered from eye diseases, leading to blindness. However, his ambition to spread Buddhism eastward became stronger and stronger and never wavered. For the sixth time in the twelfth year of Tianbao, he finally arrived in Kyushu, Japan, and in February of the following year, he arrived in Hirai Well (now Nara).
Jian Zhen was warmly welcomed by the Japanese ruling and opposition parties. Announce the award of the Bodhisattva Ring to Japanese emperors, empresses, princes and others; Awarded commandments to more than 440 people, including Misha Zheng Xiu; Give new commandments to the old commandments of 80 monasteries. Only in Japan can there be formal legal succession. Jian Zhen is regarded as the ancestor of Japanese legalists. In 756, Kejsarinnan Koken appointed him as the capital of the Great Buddhism, in charge of Japanese Buddhist affairs. In 759, Jian Zhen and his disciples carefully designed and built the Zhao Ti Temple in the Tang Dynasty, where they preached laws and precepts. He and his disciples adopted the most advanced technology in the Tang Dynasty in architecture, statues and murals, which added luster to the formation of artistic climax in the Japanese Tian Ping era. For example, the Zhao Ti buildings in the Tang Dynasty were masterpieces left by Jian Zhen and his disciples. The whole structure and decoration reflect the characteristics of the Tang Dynasty architecture, which is the largest and most beautiful building in the Japanese Tian Ping era. Before Jian Zhen's death, disciples used the latest dry painting clip technology to paint his portrait. Japan is regarded as a national treasure. 1980 in April, in order to enhance the friendship between the two peoples for generations, the Japanese-Chinese friendship group sent the seated statues back to Beijing and Yangzhou for the Japanese people and Buddhists to pay their respects. Jian Zhen and his disciples are mostly good at calligraphy. They went to Japan with the original works of Wang Xizhi and his son, which influenced them. Until now, the Japanese people still love China's calligraphy art, and most of the Japanese Buddhist scriptures were introduced from North Korea at that time, so mistakes are inevitable. According to the Japanese History, the Emperor once entrusted Jian Zhen to correct the classic mistakes. Jian Zhen's most outstanding contribution to the Japanese people is the teaching of medical knowledge, and he is honored as the ancestor of medicine by the Japanese people. Japan's tofu industry, catering industry, brewing industry, etc. I also believe that their industry skills are all awarded by Jian Zhen.