In 1335, when Ryushin celebrated his coming of age, he joined the Northern Court under Takauji Ashikaga in a war against the Southern Court. In June, 1336 Ryushin and his vanguard led an attack on the Southern Court's fort on Mt. Hiei. The fort eventually fell and the Southern Court Emperor, Go-Daigo, and his loyal vassals were captured and kept at the old palace of former Emperor Kazanin. Takauji's treatment of the prisoners was so abhorrent that Ryushin was quoted as saying "It is possible to loose the emperor from the harsh treatment he receives. I will plot his rescue." With other conspirators Ooe Gyōbu Daiyu Kageshige, Bessho Saburō Takanori (Kojima Takanori), Hiyoshi Iga Nyudō and Kisshuin Sōshin Hōgen, Ryushin broke into the palace of Kazanin and escaped to Yoshino with Emperor Go-daigo. Tadayoshi Kuragari-Tōge, the younger brother of Takauji, was alerted of the escape and sent an army of about ten thousand men in pursuit. The army caught up with Ryushin and the conspirators at Kuragari-Tōge, a mountain pass situated on the borders of Osaka and Nara prefectures. It was here that they made a stand against the army, each choosing a weapon they were proficient with. Kageshige took a sword, Takatoku a bow and arrow, and Ryushin a halberd (naginata). As the army outnumbered them completely, it was a battle of strategy and evasion; eventually the blade of Ryushin's Naginata was cut off. So Ryushin used the remains of his naginata to knock down enemies near him and put enemies at bay by swinging the staff in the air, drawing out the kuji-kiri as he did. It is said that the Bōjutsu in Kukishin Ryū was later devised on the techniques Ryushin used on this occasion. Reinforcements from Yoshino eventually arrived and they could safely take the Emperor Godaigo to a small temple-like hut located at Mt. Kinpusen. Ryushin also succeeded in re-capturing the “Three Treasures of the Imperial House” which he had concealed in a scripture-warehouse at Yokawa in Mt. Hiei.