Bratty Younger Stepsister APK is an adult-themed visual novel that explores a unique and emotionally complex relationship between two cousins living under the same roof. With a storyline that focuses on daily life, emotional growth, and forbidden affection, the game invites players to take on the role of a young male protagonist who finds himself living alone with his charming, mischievous half-sister, Kurumi, after their parents leave on a long-term overseas business trip.