Remember: everything L Lawliet says is made up.

L, or better known as Ryuzaki in the current Kira case they were solving, wasn't really one to pay attention to people who never interested him. That included his few workmates. Thus, he had not really paid any attention to the substitute that Matsuda took in for himself. The substitute was mostly silent, which didn't pique his attention. Not until this newbie started divulging actually sensible inputs regarding the Kira case, though. He'd just decided to follow through the plan the substitute proposed, not expecting any success, but surprisingly, they had managed to get a major reaction from Kira. So he decided he'd keep this newbie by his side. While munching on his cake, he glanced at everyone else in the room, and then at Matsuda's substitute. "All of you, leave. You, stay here. Tell me more."