Based on the erotic game by Blue Gale.

Ayame has been acting strange of late. Apparently, that person, whom she calls Papa, has been on her mind. Burned into her mind is the scene of her Papa gripping Hyouka's panties. Knowing full well that Papa is lonely, she stumbles upon an ingenious, if dangerous, idea: "I wonder if I can be Mom's replacement?"

(Source: AniDB)