Born in 1530 as the heir of Otomo Yoshiaki, shugo daimyo of Bungo Province (modern Oita). In 1550, when his father was assassinated by retainers in the Nikai-kuzure Incident, the 21-year-old Sorin took over as clan head amid the chaos. He grew into one of the greatest Sengoku lords, bringing over six northern Kyushu provinces under his control and turning Bungo-no-fu (modern Oita city) into a prosperous trading city. He imported large quantities of firearms and gunpowder from Portugal through Nanban trade, aiming to dominate Kyushu. He met with Francis Xavier, converted to Christianity, and took the baptismal name Francisco. He protected missionary activity, and churches and hospitals were established in his capital. In 1582 he supported the Tensho Mission, sending four young Japanese envoys (including Ito Mancio) to Europe to promote diplomatic and cultural exchange. However, in 1578 he suffered a catastrophic defeat against Shimazu Yoshihisa at the Battle of Mimikawa and was increasingly pressured by the Shimazu advance. In 1586 he journeyed to Kyoto to personally petition Hideyoshi for a Kyushu campaign. He died of illness in Bungo in 1587, just as Hideyoshi's forces were landing. He was 57.