Longjiao San is a pharmaceutical company focusing on throats and is also a well-known family medicine brand in Japan. It has a history of more than 200 years. Its main products include throat medicine, throat lozenges, and medication-assisted jelly.

"Dragon Kaeda" was a royal medicine passed down by Satakehou, the king of Akita in the Edo period, and was invented by the royal doctor of the vassal king and Genzo Fujii. The prescription at that time contained keel bone, dragon head and deer antler cream and was a powder, so it was named.

The Fujii family has been imperial physicians of the vassal kings for generations. After learning Orchid (Western Science and Technology), the second-generation descendant, Gennobu Fujii, added Western herbs to the prescription. In the early Meiji period, in order to treat the asthma of the vassal kings, the third-generation famous doctor, Masatoji Fujii, improved Longjiao San into a prescription for treating asthma, laying the foundation for the current Longjiao San prescription.

After the Meiji Restoration, due to the political reform of abolishing the vassal state, the vassal kingdom disappeared. Fujii Masatoi, who moved to Edo (now Tokyo), was granted "Ryukaku San" by the vassal king. In 1871, he was awarded "Ryukaku San" in Kanda, Tokyo. Pharmacies are opened in the area. The "secret medicine" exclusive to the vassal kings has also been transformed into a product sold to the general public. In 1893, the fourth generation of Fujii Tosaburo further improved the "Rongjiao San" and ground several herbs into 10-20μm micro powder and mixed and processed, achieving the current "Rongjiao San".