Tesso (éÂÂé¼ ) is a Japanese yà Âkai related to the vengeful spirit (onryà Â) of the Heian period monk Raigà  and a mouse. The name "tesso" is a name given by Toriyama Sekien in the Edo period collection of yà Âkai pictures, the Gazu Hyakki Yagyà Â, and this yà Âkai can also be called the Raigo-derived name Raigà Â-nezumi (頼豪鼠) as from the Enkyà Âhon (延栶æ¬, alternatively read Enkeihon), a yomihon version of the Heike Monogatari, or Mii-dera-nezumi (ä¸ÂäºÂ寺鼠) derived from Mii-dera in à Âtsu, Shiga Prefecture as in the Edo period yà Âkai themed kyà Âka picture book, the Kyà Âka Hyaku Monogatari. They became known starting in the Heisei period from its adoption in the mystery novel Tesso no Ori (The Tesso's Cage) by Natsuhiko Kyogoku.
According to the Heike Monogatari, in the Heian period, Raigà Â, on the basis of a promise with Emperor Shirakawa of receiving as much reward as desired if it had effect, continuously prayed for the birth of the emperor's crown prince, and in 1074 (in the Jà Âhà  years) on December 16, it was finally succeeded. As a reward, Raigà  requested for the construction of an ordination platform (kaidan) building for Mii-dera, but opposition forces from Enryaku-ji at Mount Hiei obstructed this and prevented it from being granted.
In resentment, Raigà  then proceeded to make prayers to drag the crown prince who was born from his prayers, Prince Atsufumi, down to the clutches of evil, and went into a fast. After 100 days, Raigà  ended up looking like an evil ogre and died, and starting since then, an ominous white-haired old priest would appear by Prince Atsufumi's pillowside. Emperor Shirakawa was fearful of Raigà Â's curse and grasped around for prayers, but they had no effect, and Prince Atsufumi died barely at the age of 4.
In the yomihon versions of the Heike Monogatari such as Enkyà Âhon (延栶æ¬, alternatively read Enkeihon) and Nagatohon (é·éÂÂæ¬) and in the different book Genpei Jà Âsuiki, among other sources, the grudges of Raigà  became a giant rat and ate away at the sacred books in Enryaku-ji. Enryaku-ji was fearful of Raigà Â's grudge and built a shrine at Higashisakamoto to enshrine Raigà  as a god in order to quell this grudge. The name of the shrine has been passed down to be "Nezumi no Hokura" (é¼ ã®ç§ÂÃ¥ÂÂ, The Rat Shrine). It is also said that after this, large rats have been called "Raigo-nezumi."
According to the military chronicle (Gunki monogatari) Taiheiki, the grudges of Raigà  turned into 84,000 rats with stone bodies and metal teeth and climbed up Mount Hiei and ate away at not just the sacred texts, but also the Buddha statues.
In the late Edo Period, the yomihon author Takizawa Bakin wrote Raigà  Ajari Kaisoden (頼豪é¿éÂÂ梨æ 鼠ä¼Â) based on the Raigà  legend. While the elegant Shimizu Yoshitaka (水義é«Â, also known as Minamoto no Yoshitaka or æºÂ義é«Â), the orphan of Kiso no Yoshinaka was traveling across several provinces, Raigà  appeared to him in a dream and talked about how because Yoshinaka once contributed a request form to Raigà Â's mini shrine (hokora) to become Seii Taishà Âgun, so he will offer his help to Yoshinaka, and told him about how Nekoma Michizane has been targeting his life due to having a grudge against him, and instructed Yoshinaka on some rat sorcerery.
In the story, the scene when Mitsuzane tried to cut down Yoshinaka and a giant rat appeared and stopped this, the scene when Yoshinaka called out an eerie person with the face of a rat in order to lure out his father's enemy Ishida Tamehisa, and the scene when Yoshinaka stopped Michizane's torture of his mother-in-law by summoning countless rats, among other scenes, were all given illustrations by the ukiyo-e artist Katsushika Hokusai.
In history, Raigà  died in 1084 and Prince Atsufumi died in 1077, meaning that Raigà Â's death comes after Prince Atsufumi died, which is not consistent with the story, leading many specialists to posit that this legend is clearly made-up fiction.
However, certain parts, such as Mii-dera's request to the emperor for the construction of an ordination platform building, the prolonged declining of this request due to opposition from Enryaku-ji, and Raigà Â's efforts at getting this ordination platform building built, are seen as historical fact. Furthermore, according to the Jimon Denki Horoku (寺éÂÂä¼Âè¨Âè£Âé²), the temple records of Mii-dera, as a result of the imperial court not approving the request to the emperor to build the ordination platform building, Raigà  fell into gloom and did not leave the temple, resulting in a great rumble at the Shinra shrine at Mii-dera. Both Mii-dera and Enryaku-ji were in the Tendai sect, and after the death of the founder of the sect, Saichà Â, the sect split into two factions that engaged in violent disputes, and Enryaku-ji has had a history of being burned down several times as a result, so it is thought that this Tesso legend was born from the background of the confrontation between the two factions of the Tendai sect at that time.
Furthermore, stories in which not just metal rats (tesso), but also rats in general cause harm to people can be found in the Tà Âhoku region, the Nagano Prefecture, and other places all over Japan, but this is interpreted to be because in the past, rats did cause a lot of harm, and temples that held many books and sacred texts had some serious problems with rats causing damage, so there is the view that the existence of rats became the basis for legends about vengeful spirits and yà Âkai.
The "Nezumi no Hokura" noted in the Heike Monogatari to be for calming the vengeful spirit of Raigà  exists at the Hiyoshi Taisha in Sakamoto, à Âtsu, Shiga Prefecture. However the Keizai Zasshisha (ç¥ÂéÂÂç§Âå¯Âè¨Â) written in the AzuchiâÂÂMomoyama period at the Hiyoshi Taisha notes that the "Nezumi no Hokura" enshrines the Rat of the Twelve Earthly Branches. The way the Nezumi no Hokura is talked about in relation to Raigà  is seen to be because as previously noted, rats were actually a source of misfortune bringing harm to people, or because Enryaku-ji was in the kimon (demon's gate) direction from Kyoto resulting in a lot of sorcerery activity in the past and Hiyoshi Taisha is there to protect against that, leading to legends about neutralizing vengeful spirits to take root.
It appears that the Nezumi no Hokura had already become famous by the Kamakura period, and in the Isetsu Hishà  Kuden no Maki published in 1319 (in the Gen'à  era), there is the lyrics "At the base of Wagatatsusoma (meaning Mount Hiei) is a rat god, and by sounding its name once again, maybe it'll bring forth some good fortune" (ãÂÂãÂÂã°ãÂÂæÂÂç«Âæ£ã®éºÂã«ãÂÂé¼ ç¥Âã¨ãÂÂã¯ã¯ãÂÂ給ã²ã¦ãÂÂå ¶åÂÂãÂÂãÂÂãÂÂãÂÂã«ã¨ã©ãÂÂãÂÂãÂÂæ§Âã ã®å¥ÂçÂÂãÂÂãªãÂÂãÂÂã¨ãÂÂ) and in the renga collection Tsukubashà « compiled in the Nanboku-chà  period, there are renga based on the Raigà  legend such as "this is the rat around the mountain base" (塵ã«ã¾ãÂÂã¯ãÂÂé¼ ã¨ãÂÂãÂÂãÂÂãÂÂ) and "at our mountain, it is one of the gods worshipped" (æÂÂå±±ã«ãÂÂãÂÂãÂÂãÂÂãÂÂãÂÂãÂÂç¥Âã®ãÂÂã¡), among others. Originally, this hokura (shrine) was told to be bringing benefit by warding off rats, but starting in the Shà Âwa and Heisei periods when anti-rat measures have started to become sufficient, it has gradually lost its role of warding off rats.
The Jà «hachi Myà Âjin (Ã¥ÂÂå «æÂÂç¥Â) to the side of the stone steps at Mii-dera is also called "Nezumi no Miya" (Rat Palace), and it is said to pacify the spirit of the Tesso and others, and it is built facing the direction of Mount Hiei.
Another idea is that the Tesso was slain by a big cat who appeared because of the Buddhist power of a high priest at Mount Hiei, and towards the "Nezumi no Miya" at Mii-dera, there is the "Neko no Miya" (Cat Palace) deifying the big cat at Sakamoto in Sakamotogà Â, Shiga District, à Âmi Province, known to be the town in front of the Enryaku-ji gates, where it is built glaring in the direction of Mii-dera.
In a legend in Shimotsuke Province (now Tochigi Prefecture), it is told that 84,000 rats went around several provinces ravaging the fields, but when the rats tried to attack Shimotsuke, Shà Âgun Jizà  (Ã¥ÂÂè»Âå°èµ, general jizà Â) appeared and stopped this, and sealed them in a mound. According to "Oyama no Densetsu" (Legends of Oyama) by the Oyama City Area Cultural Research Society (å°Âå±±å¸Âé·åÂÂæÂÂÃ¥ÂÂç Â究ä¼Â), this mount is the Atagozuka (æÂÂå®Âå¡Â) in Dotà Â, Oyama, and another name for it is "Raisozuka" (æ¥鼠å¡Â, Come Rat Mound) and it is said that within it is a cave where rats were sealed inside. It is also said that by taking a rock from on top of this mound and leaving it in a field, it can avoid any harm due to rats.