 The two most important mantric syllables from Sanskrit – in the Siddham (Jpn: shittan) script system popularized in East Asia – emphasized in Shingon Buddhism, in both sound and graph, are A and Un (Hūṃ). The former is the seed-syllable of Dainichi as explicated in the Dainichi-kyō and the latter is the seed-syllable of the Kongō-satta (Vajrasattva, a buddha-being believed to have received instruction directly from Mahāvairocana) as explicated in the Kongōchō-gyō, and together seen as non-dualistic in significance. In the following I will discuss the significance of these seed-syllables.