The kuji-in () or jiǔzìyìn (), also known as Nine Hand Seals, is a system of mudras and associated mantras that consist of nine syllables. The mantras are referred to as kuji (), which literally translates as nine characters. The syllables used in kuji are numerous, especially within Japanese esoteric Mikkyō.
Scholars have stated that kuji is of Taoist origin, not Buddhist. There is no mention of the kuji in any of the Shingon or Tendai records that were brought back from China. [citation needed] The use of kuji is essentially a layman's practice and is uncommon in many orthodox Buddhist traditions. It is, however, found extensively in Shugendō, the ascetic mountain tradition of Japan and Ryōbu Shintō, which is the result of blending Shingon Buddhism and Shinto.
History
The kuji are first introduced in the Bàopǔzǐ (), a Chinese Taoist text written by Gé Hóng c.280–340 CE). He introduces the kuji in chapter 17, entitled Dēngshè (登涉; lit. "Climbing [mountains] and crossing [rivers]), as a prayer to the Liùjiǎ (六甲; Six Generals), ancient Taoist gods. In Daoist Magic, the Jiǎ are powerful celestial guardians and are among the gods of the Celestial Thunder Court of Emperor Xuanwu.
The kuji are first seen in line 5 which reads,
抱朴子曰：“入名山，以甲子開除日，以五色繒各五寸，懸大石上，所求必得。又曰，入山宜知六甲秘祝。祝曰，臨兵鬭者，皆陣列前行。凡九字，常當密祝之，無所不辟。要道不煩，此之謂也。”
Translation:
The kuji form a grammatically correct sentence in Classical Chinese. They come from this section of the chapter and are written as which can be roughly translated, "(Celestial) soldiers/fighters descend and arrange yourselves in front of me", or "May all those who preside over warriors be my vanguard!"
Other translations are possible as well, as variations exist in Japanese esoteric Buddhism. According to the Baopuzi, the kuji is a prayer to avert difficulties and baleful influences and to ensure things proceed without difficulty. To this end it can be said that the primary purpose of kuji is abhisheka (正灌頂, ) and exorcism (調伏, ).
The Taoist kuji are next cited in a text called The commentary on the discourse about the Sutra on Immeasurable Life, and on the verses about the vow to be reborn [in the Pure Land] (無量壽經優婆提舍願生偈註, Wúliàng shòu jīng yōu pó tí shě yuàn shēng jì zhù), also known as the Commentary on the treatise on rebirth in the Pure Land (往生論註, Wǎngshēng lùn zhù) written by Taluan (467?–542? CE).
How the kuji arrived in Japan is still a matter of debate. The Korean variant is 臨兵鬥者皆陣列在前行. Some contemporary scholars assert that the kuji arrived in Japan via China through Jōdo-shū and Shugendō around the 8th century, if not much later. Others assert that they were introduced by Korea. As to what the kuji consisted of at the time it arrived in Japan is unknown. The mudras are found in Taoist material as well as in Shugendō. Some have suggested that Shugendō created the mudras that are currently associated with the kuji, as the vast majority of information that is known about the kuji comes from Shugendō literature.
Ryobu kuji
The earliest known Japanese application of the kuji comes from the Shingon monk Kakuban (1095–1143 CE) who was an academic of Taluan's writings and teachings. Kakuban introduced several kuji formulas dedicated to Amitābha, in his text The Illuminating Secret Commentary on the Five Chakras and the Nine Syllables (五輪九字明秘密義釈, Gorin kuji myō himitsu gishaku or 五輪九字 Gorin kuji hishaku).
The kuji formulas Kakuban introduces are commonly grouped under the title zokushu, and are completely unrelated to original Taoist kuji. The monk Shinran (1173–1263 CE), founder of Jōdo Shinshū sect, introduced several new kuji formulas, also dedicated to Amitābha. Nichiren, founder of the Nichiren sect, introduced a kuji prayer derived from chapter 26 of the Lotus Sutra, where it is uttered by the god Vaiśravaṇa.
Neither the founder of Shingon, Kōbō Daishi, nor the founder of Tendai, Saichō, mentioned the kuji in any of their writings. It may be assumed that they were unfamiliar with the kuji or only considered them as part of a minor teaching. Regardless, the nine syllables of the kuji have developed several correlations and associations with religious and philosophical aspects of Japanese esoteric Buddhism. They are associated with the five chakras (五輪, gorin), the five elements (五大, godai), certain directions of the compass, colors, and deities.