[Beyond takes a few steps back of his own, much more guarded now that he isn't at point blank.]

I've already made one promise today, isn't that enough for you? How about I do you the favour of keeping it our little secret. That should satisfy you, shouldn't it?

[He's probably still walking a thin line, but he has no intentions of making that promise to Mello. That name is a trigger point, it's leverage. And he'll willingly tread that line.]

Or I can swap the promises, if you prefer - take back the word to not attack Sharon and choose not to call you by your name.

[Try him, Mello. He's practically daring you.]