Miyatsu

is the paternal grandfather of Miroku, who was cursed by Naraku.

History
Miyatsu had been in a long fight against the Hanyō Naraku for years. Each time they fought, Naraku took on the form of a different person. Naraku cursed Miyatsu (At that time disguised as a woman) 50 years ago. He was the first in his line to bear the Wind Tunnel (Kazaana). In InuYasha the Movie: The Castle Beyond the Looking Glass, it is revealed that it was he who sealed Kaguya within her own mirror.

Personality
According to Miroku, Miyatsu was, like his son and grandson, quite the ladies' man (aka a lecher).

Powers & Abilities
Though not often mentioned throughout the series, Miyatsu is depicted as having immense skill as a holy-man and powerful spiritual abilities. Nark apparently feared his Spiritual Powers to the point that he would curse him.

Weapons

 * Kazaana: The Wind Tunnel is a curse placed upon Miyatsu by Naraku that would be passed down through the male line in his family. The curse pierced the palm of the monk and resulted in a hole or void into another dimension which sucks everything into it, creating a terrible sucking wind in the process. The Wind Tunnel also suppressed some of his Spiritual Powers.
 * Sacred Sutras: These "Jufu Talismans" are strips of paper upon which special prayers have been written and prayed over, imbuing them with spiritual power and energy against specific evil. Each Ofuda has a special prayer, and thus is tailored for a specific purpose such as general protection, good luck, safe travel, removing a ghost or spirit, or sealing off a demon or spirit. Miroku uses them in his work to "exorcise" ghosts and demons from homes and people.

Reference
Miyatsu Miyatsu 弥萢