This was always a somewhat difficult part, something that Watari had handled in the past. The very nature of L's gift required that he kept a somewhat low profile, and so it could be sticky and awkward when he was put in a position where his identity could be compromised. He didn't give away his name... or anything else... freely.
"Because he has something to do with the kidnapping," he said quietly, keeping his voice low. Someone with a spirit as pure and clean as this member of the order would not hurt him; he was 100% certain, but old habits were a bitch to kick. He said only as much as he had to, before adding in a meaningful tone, "Trust me. I'd stake my life on it."