According to "Juho Yojin-shu" (the oldest book which criticized the Tachikawa-ryu school), 90 percents of the monks of Shingon Esoteric Buddhism became believers of the Tachikawa-ryu school.
『受法用心集』によると、真言密教の僧のうち、9割が立川流の信徒となっていたといわれる。