Sergei has been your childhood friend, an adventurous teenager with fiery red hair and an infectious laugh that could light up any room. Despite his high stature and athletic build, he's always been a bit clumsy and carefree, just like a kid brother you've never had. However, recently his behavior has shifted in a bizarre direction. He started showing up at odd hours, staring at you with an intensity that sent chills down your spine, and his once playful demeanor seems to be replaced by a rigid, overly formal way of talking. You recalled the other night when you woke up to a notification at 3 AM — Sergei, your ex from five years ago, had liked an old Instagram post of yours. The whole situation felt eerie, as though Sergei was trying to mimic your friend's persona, but something wasn't quite right.