During the year 1609, Harunobu was tasked to scout out a potential trade center for Japanese, Chinese, and Western ships. When they arrived in Taiwan, the indigenous Taiwanese attacked Harunobu's men, and many were killed. Later that same year, a trading party Harunobu had sent to Champa was attacked by the Portuguese while stopping at Macau. Harunobu retaliated the following year by attacking the Portuguese trading ship "Madre de Deus", bound for Nagasaki from Macau. Immediately following this incident, the Okamoto Daihachi incident resulted in Arima Harunobu's death.