Secretly With My Oppa's Friend summary: After repeatedly being dumped by men for strange reasons, Jisoo ends up dating Taejun, her older brother Jisung’s friend. She keeps the relationship a secret from Jisung. Jisung, Jisoo, and Taejun end up drinking together at home. Having been together for just a month, Jisoo and Taejun can't keep their hands off each other— just locking eyes sends sparks flying. Even at home, with Jisung right there, they sneak chances to indulge in their desire. Will their risky secret affair stay hidden until the end?