Answer: American business interest.
Step-by-step explanation:
The Japanese authorities signed the Kanagawa agreement under the US threat. This agreement ended Japan's isolation from America primarily. Japan pursued a policy of separation from the rest of the world. The agreement promised security for US citizens and established a consulate in Japan.
This move by the US government was primarily to protect the business interests of American citizens on Japanese soil. By signing this treaty, the Americans could fearlessly engage in trade and other activities on Japanese ground.