Saint Elna and the Book of Depravity ~The Sex Duties of the Busty Sister~

Elna, the busty sister of Ulunka Village. - One day, she receives a request for assistance from another village and sets off for "Adus Village," far from her hometown. - There, she is tasked with watching over "Lenis the Incubus," said to have been sealed in the village's cave since ancient times. - Upon visiting the cave, Elna discovers an old book deep within. - As Elna approaches, the book suddenly emits a strange light, - and the sealed incubus is inadvertently released.