Mizuchi 蛟 are a type of oriental dragon, or sometimes legendary serpentine creatures. They are often related to water and may dwell in aquatic environments. Many scholars have described them as water deities. They have been described in the Chronicles of Japan Nihon Shoki as well as in some of the poems of the Man'yōshū.
The term Mizuchi is the Japanese reading of several types of Oriental dragons, including the jiaolong (蛟; kōryū) "four-legged dragon," the qiulong (en) (虬; kyūryū) "hornless dragon," or the chilong (螭; chiryū) "yellow dragon."
Daniels (1960:157) noted that Japanese serpentine deities who had the ability to control rain were sometimes called "dragons." However, he asserted that it would be unwise to describe the forms of "okami" and "mizuchi" as the same as those of the Chinese creatures associated with them.
The Chronicles of Japan Nihon Shoki refers to mizuchi. During the 67th year of Emperor Nintoku's reign (in 379), it is told that in Kibi province, at the diffluence of the Kawashima River (川嶋河, the former name of the Takahashi River in Okayama Prefecture), a large snake or dragon (大虬) dwelt, expiring or spitting out its venom, poisoning and killing many passersby.
This "mizuchi" was reportedly killed by a man named Agatamori (県守), an ancestor of the Kasa-no-omi (笠臣) clan. He approached the river and threw three gourds that floated to the surface of the water, he then challenged the creature to sink the gourds, threatening to kill him if he failed.
The creature turned into a deer and tried unsuccessfully to sink them. Thus the man killed the creature. It is also said in the Chronicles that "the man then sought out the creature's fellow creatures. The "water dragons" took refuge in a cave at the bottom of the river, before the man caught up with them and killed them all.
The water in the river turned to blood. Thereafter, the river was named Agatamori" (Aston 1896: 1, 299; orig. JHTI 2002). A river god seen in the 11th year of Nintoku's reign (year 323) is also considered by scholars to be a mizuchi, especially because of the similarity of its appearance with other stories. In that year, breaches kept appearing on the Mamuta (茨田堤) dikes along the Yodo River.
The emperor, guided by an oracular dream, ordered that two men, Kowa-kubi from Musashi province and Koromo-no-ko from Kawachi province, be sacrificed to the river god Kawa-no-kami (河伯). One of the two men resisted the sacrifice and challenged the river god to sink the calabash that was floating on the surface of the water in order to find out if his sacrifice came from a divine will or not.
The god tried to sink it with a whirlpool but failed. Thus, the man escaped death. Although the river god is not called "mizuchi" in the source of this story, Aston asserts that they are equivalent (Aston 1905: 1, 150-151). De Visser (1913:139) concludes, "From this passage we learn that in ancient times human sacrifices were made to dragon-like river gods." Foster (1998:1) suggests that this may be "perhaps the earliest occurrence of the water spirit, today better known as kappa."
In Japanese mythology, the "kappa" is described as a water imp that can be malicious, unlike the mortal dragons mentioned above. However, the "kappa" can be sinister in nature, it would sometimes break into the bodies of humans to steal their liver or "Shirikodama (尻子玉)".
Another mizuchi is mentioned in the Man'yōshū, the first anthology of Japanese poetry, with the tanka composed by Prince Sakaibe (境部王), "Oh if only I could ride a tiger to pounce on the old hut, go to the greenish river and capture the mizuchi, with a sword" (Man'yōshū, Book 16; Yoshimoto 1998).
In the prologue to his study named Jūnishi kō: mi (hebi)|『十二支考・蛇』| "A Study of the Twelve Animals of the Chinese Zodiac: the Snake," Minakata Kumagusu states that "even in [his] country (Japan), the many scary snakes related to water would have been called 'mizuchi,' or 'water masters.'" (Minakata 1917).
According to him, the suffix "-chi" in "mizuchi" would mean "nushi" or "den-master of lakes", however the historian Motoori Norinaga later claimed that "-chi" was an honorific particle (Minakata 1916).
To clarify his point, Motoori (Kojiki-den, 1822) added that the root of the "-chi" suffix was a tatae-na (讃え名, "name of worship") and that it can be found in the name of the great snake Yamata-no-Orochi as well as in the names of the victims of the same snake, namely Ashinazuchi and Tenazuchi (ja) (アシナヅチ・テナヅチ).
Minakata also thought that "tsuchi" and "chi" might have meant "snake" in view of the name of a Japanese snake called yamakagachi (Rhabdophis tigrinus) (Minakata 1916, "Dragon"). The famous folklorist and Minakata acquaintance Kunio Yanagita believed that the word "tsuchi" meant "spirit" (Minakata 1916 and Yanagita 2004, 32;573)
Minakata noted variants of the word "mizuchi" in local dialects, such as "mizushi" (Ishikawa Prefecture), medochi (Iwate Prefecture), mintsuchi (Hokkaidō). Asakawa Zenan (Essay, vol. 1, 1850)7 mentions the word medochi (Ehime prefecture) and the word mizushi (Fukui prefecture).
However, these words were found to be local names for kappa. However, Minakata notes that the legend of kappa comes from tales about the "nushi" (den-masters of water) who transformed into humans to harm them. These origins, however, have been forgotten. Folklorists such as Yanagita and Junichiro Ishikawa share this view.
Minakata also gathered a number of insights into local traditions throughout Japan concerning aquatic snakes capable of killing humans. He was able to establish a link between these snakes and the legend of the kappa, which is said to extract the "shirikodama" or the fabulous organ belonging to their victims through the anus.
This link seems to be consistent with his view of the word "mizuchi", originally associated with aquatic snakes and later associated with kappa.
Until the Edo period, Japanese experts relied on classical Chinese encyclopedic texts and natural history treatises. One of the widely cited references is the Honzō Kōmoku or Bencao gangmu (本草綱目) in Chinese, the compendium of Chinese medicine considered the most comprehensive. It refers to the "dragon jialong":
蛟龍【釋名】時珍曰︰按︰任 《述異記》雲︰蛟乃龍屬龍；有翼，曰應龍；有角，曰虯龍；無角，曰螭龍也。(Li Shizhen, Chapter: Scales (Part 1))
Li Shizhen: Ren Fang's Shuyi Ji book: Jiao is a type of dragon. When its eyebrows cross, it is called Jailong (Jiao ≅ met). The Jialong has scales. The species having wings is called Yinglong. The species with horns is called Qiulong and the species without horns is called Chilong ... (tr. Luo Xiwen (2003), p.3508)
When this text is read in Japanese using Kanbun, it reads "The mizuchi is a type of dragon..." Indeed, the character 蛟 (jiao) can be read as "mizuchi" when read in "kun'yomi", the Japanese reading of kanji. Other Chinese dragon names such as qiulong (虬 or 虯; Japanese: kyū; pinyin: qiú) and chilong (螭; Japanese: chi; pinyin: chī) can be read "mizuchi" in Japanese.