안전한 오빠

After breaking up with her trashy, good-for-nothing ex-boyfriend, Song A-Yun gets a recommendation for a dating app from a friend. She starts chatting with a user called "Smiling Man" and even ends up having phone sex with him! However, something feels off—the Smiling Man's voice sounds strangely similar to her friend's older brother, Ju Sang-Hyeon. A-Yun checks the app and sends a message, just in case... and then Sang-Hyeon's phone rings! A-Yun initially believes she is safe because she assumes he has no interest in her, but as she watches Sang-Hyeon pursue her with relentless, forward momentum, she realizes too late: This man is not safe at all!