On Decemebr 21 in the same year, when the Adachi clan was destroyed by the Shimotsuki Incident, which was led by the conflict between Yasumori and Uchi-Kanrei (head of Tokuso Family) TAIRA no Yoritsuna, Morimune who was in northern Kyushu secluded himself in Iwato-ji Castle with Kagesuke SHONI, and fought with a troop of Kagesuke's brother, Tsunesuke SHONI, which backed Yoritsuna, but was defeated and dead (battle in Iwato).
同年11月17日、泰盛と内管領平頼綱の対立による霜月騒動で安達一族が滅ぼされると、北九州にいた盛宗は少弐景資と共に岩門城に籠もり、頼綱方である景資の兄少弐経資の軍勢と戦って敗死した（岩門合戦）。