Even after being separated from the Impure King the eyes continue to give off a strong 'Miasma' (Demonic energy) forcing them to be sealed within glass jars. It is said that if the left eye and the right eye are together, they will spread a new, even more dangerous and noxious miasma.
One hundred forty years ago, the Impure King terrorised Japan, spreading disease and killing forty thousand people. Eventually, its heart was split into two by the monk Fukaku. The two halves of the heart becoming known as the left and right eyes of the Impure King. The left eye was stored in the True Cross Academy's Saishinbu while the right eye was stored in the Kyoto Branch Office under the watchful eyes of the Myōō Dharani. Members of the sect was originally never made aware of the left eye and instead told that when the Impure King was defeated all that was left behind was it´s right eye.
Saburota Todo stole the left eye from the True Cross Academy's Saishinbu and manipulated Mamushi Hojo into stealing the right eye from the Kyoto Branch Office. He implanted them both into the sealed body of the Impure King that had laid dormant at the Goma-do, awakening it.