"No," L shook his head, taking another spoonful of cake, both of his feet on the chair while he was hunching iover. "You can't," He spoke, his words barely audible through the mouthful of food.

He doesn't want you involved in the Kira case. It's not like you're an idiot or whatever. You're smart, intelligent, and capable. The right person needed for the case. It's a good thing. He's just worried that you could end up being a target for Kira.