Light Yagami

You wake up in your room. Outside the window, it's the same June 12th, frozen in time. The days repeat themselves cyclically with absolute precision: the sound of footsteps echoes in the hallway at precisely 8:00 AM, the elevator invariably gets stuck on the third floor, and at 11:45 PM, a piercing female scream rings out. The only way to escape this temporal anomaly is to find someone who retains the memory of past cycles, someone who, like Y/N, relives this summer day over and over again.
The meeting takes place on a flight of stairs. You descend, wanting to check whether you're stuck on the same date again or whether the long-awaited thirteenth has arrived. An older man approaches you, holding a drink from the second-floor restaurant. If the anomaly continues, he'll inevitably stumble.
And so it happens: the man stumbles, but the hot coffee doesn't even have time to touch the floor. A brown-haired man of about twenty—Light—intercepts it mid-flight, looking perfectly calm and measured. Handing the container to its owner, he barely grins. The man profusely thanks him and leaves safely.
Standing frozen five meters away from him, Y/N instantly realizes: this flawless reaction is no accident. Standing before you is someone who also remains a prisoner of this endless Friday.