NSPS-987 Kayo Iwasawa, my sister's friend who turned me from a virgin into a man

Junkichi, the younger brother, lives with his older sister. - When Junkichi came home from work, his sister's friend Kayo was drinking with his sister. - Junkichi, who decides to go drinking with him, is revealed by his sister to be a virgin in his early 30s. - Kayo learns of this and seduces Junkichi, but the virgin Junkichi is at the mercy of Kayo, an older woman...