In 1185, after Yoshitsune destroyed the Taira at Dan-no-ura, Yoritomo barred his brother from entering Kamakura, angered by his unauthorized acceptance of court titles. Detained at Manpukuji, Yoshitsune wrote the celebrated "Koshigoe Letter" to aide Oe no Hiromoto, pleading his loyalty—but Yoritomo's heart remained unmoved, setting Yoshitsune on a path toward his tragic end.