TESSO

Lore

The legend of Tesso (literally "Iron Rat") connects to a real historical figure: the Buddhist monk Raigo Ajari. His story is documented in Buddhist chronicles, which tell of Emperor Shirakawa, fervently longing for an heir. Hoping for divine favor, the emperor requested the head priest of Mii-dera to have his monk, Raigo, pray day and night for the birth of a son. Renowned for his piety and spiritual power, Raigo took it upon himself, with utmost devotion, to help the emperor. When Emperor Shirakawa asked Raigo what reward he desired if the prayers were successful, the monk asked that Mii-dera be allowed to take on fifty new novices, thereby expanding the temple.

After many nights of prayer, Fujiwara no Kenshi conceived, and Prince Taruhito was born. However, when it came time to grant the promised reward, complications arose. Rival monks from Enryaku-ji pressured the emperor to renege - their motives uncertain, though likely driven in jealousy and unwillingness to let Mii-dera become the dominant temple of Shiga Prefecture. Feeling betrayed and enraged, Raigo declared a hunger strike to protest the ruler's injustice. In the end, he died, cursing the emperor and his bloodline. Rumor has it that, in his final days, Raigo lost his grip on sanity, casting dark curses on all his adversaries in the neighboring temple and praying to demons.

According to temple records, this fast lasted precisely one hundred days. When Raigo died, his vengeful spirit found no rest in the afterlife, transforming him into a monstrous being: an iron rat with unbreakable hide and vicious fangs. Locals called this creature "Tesso," a hybrid of rat and human.

In this new incarnation, Tesso gained dominion over rats, amassing swarms from across the province for one purpose: the annihilation of Enryaku-ji. The rat army laid waste to nearly all the temple's sacred scrolls and relics, with Tesso's ambition not just to destroy Enryaku-ji but to erase every trace of it over time, so no one would ever speak of it again. The chronicles are silent on the monks' fate that dreadful day, though it's not hard to imagine how few survived such an overwhelming infestation, even within temple walls. No one knows exactly how this story ends. The demonic entity, Tesso likely did not simply vanish once the temple lay in ruins. Some say he never truly disappeared, persisting as a yokai: a half-rat, half-human specter, a grim spirit lurking.