Due to his long imprisonment (with lack of space for sleeping and sitting), Yoshitaka suffered a leg disorder and lost his eyesight in one eye for the rest of his life.

After seeing the thriving Christian population of Kyushu, under Ukon's influence, Yoshitaka was baptized with the name ドン・シメオン (Dom Simeão = Don Simeon).

After a visit to the Jesuit-controlled port of Nagasaki, Hideyoshi became fearful of the powerful influence that Jesuits and the Christian daimyōs wielded.

In 1587, he made his famous edict that expelled foreign missionaries and ordered all the Christian samurai under his rule to abandon their faith.

While Ukon resisted the edict and lost his status, Yoshitaka gave up his new religion and adopted a monk's habit, calling himself Josui (如水).

[9] It was recorded that Yoshitaka and his son, Nagamasa, bore grudge towards Mitsunari due to their personal conflict with him and alleged mismanagements during the Japanese invasions of Korea (1592–1598).

[10] In 1600, Yoshitaka was seemingly on the Tokugawa side during the Sekigahara campaign, having clashed against Ōtomo Yoshimune at the Battle of Ishigakibaru and also, having participated at the Siege of Yanagawa.

As depicted in historical writings and contemporary television, it is suggested that Kuroda was simultaneously feared by Hideyoshi, despite his attempts to hide his intelligence and influence.

In addition, Kuroda deepened a friendship with Sen no Rikyū, known as the founder of the Japanese tea ceremony "wabi-cha", and who was later put to death by Hideyoshi himself.