Adult PC Game: Bern's Breeding Sim v1.0 by Outis Media Archive

Overview:
(YOU) are the player, a dutiful, albeit slightly boring guy who works hard and does his best. Fate throws a wrench in your mundane plans for the future when your little sister asks you a huge favor: take care of her harpy friend, Bern.

The harpy herself is unimposing and shy, and cute as a button to boot. Maybe she's not a burden at all, and something may blossom, between the two of you...