Enenra (煙々羅 en'enra, lit. "lightweight fabric smoke") is a Japanese youkai that is described as a spirit composed of smoke which resides in bonfires or rises out of houses, taking the form of a human. It is also said that an enenra can only be seen by the pure-hearted.
Enenra in Touhou
In Forbidden Scrollery, after a "word-eating worm" eats one of Hieda no Akyuu's scrolls, Akyuu and Kosuzu Motoori unseal an enenra from the Hieda manuscript of Gazu Hyakki Yagyou in order to smoke it out.
However, the enenra escapes and goes around Gensokyo possessing households, being transferred through sight. When Reimu Hakurei and Marisa Kirisame go to Kosuzu for answers, she lies and says the enenra escaped after the word-eating worm ate the page it was located on, but tells them how to defeat it. Physical attacks don't work, but by burning items youkai don't like in a targeted house, it caused a sacred smoke and finally allowed them to reseal the youkai after a days long chase.
- Wikipedia entry for Enenra