In 1910 he became Master of Chilburam Meditation Hall on Jirisan mountain, and his congregation asked him to critique others religions from a Buddhist standpoint. This resulted in his writing of a treatise known as Gwiwon Jeongjong, a work which focused primarily on the flaws of Christianity. In 1911 he left for Seoul, where he found himself dismayed by the situation of Korean Buddhism when contrasted with other religions. So he began teaching Buddhism to others while there, and established Daegaksa and other temples while there. He also managed a mining company to help fund some of his Buddhist missionary work. In 1919 he became involved in the Korean Independence Movement, and was named one of thirty-three national representatives for the March 1 Movement—the designated representative of the Buddhist community. He was arrested by the Japanese during this event and detained until 1921. Following his release, Yongseong doubled his efforts to propagate Buddhism in Korea, and in 1925 he established the Supreme Enlightenment Foundation—an organization which sought to establish Buddhist educational movements. He spent the remainder of his life spreading Buddhism, and died in 1940 at age 76.