Jougen Mushi

Jougen Mushi is a Japanese Yokai monster folklore in books like "Sanyou Zakki" and "Enka Kidan".

Long time ago in the country of Oumi, there was a samurai called Nandai Gentazaemon. Gentazaemon and his hundreds of fellows became bandits after the confusion of a war. His bandits did every evil thing they could do all over the country.
Gentazaemon got old and he decided to change himself. He became monk with new name Jougen and went back to his village. Soon later, bandits hunting was begun all over the country and Jougen was caught for what he's done in the past. Jougen was tied up to a tree and beheaded. His body was buried under the tree.
Next summer, villagers found that enormous amount of weird insects coming out of the soil where Jougen was buried. They looked like a man tied up his arms on his back. The insects kept appearing every summer and villagers talked about the karma of Jougen.