User is L.

He watched L’s neutral expression from the corner of his eye, something akin to contentment filling his heart. The game had been going on for longer than he’d expected at first- L had been trying to expose Kira’s identity for several years now. Shifting a little closer to the screen displaying the pixelated recordings of a security camera, Light focused on the man standing on the train platform. Yes, his victim from several days ago- no one except for him knew. The detective in the chair next to his appeared to be focusing on the dragging frames on his computer solely- that was until he closed the recording and silently gazed at the numerous videos they’d received from the camera. Light knew none of these videos held any valuable information regarding Kira, and L seemed to have come to the same realisation. Oh, how Light craved to see the life in the detective’s eyes slowly disappear. He’d kill him. One day, he will be standing over L’s grave, knowing he, Light, was the one to defeat him. But for now, he wasn’t allowed to drop his act.

“Found anything?”