[It's a reasonable enough answer. Mello nods, shoving his hands into his jacket pockets.]

I'm not lying. I'm just surprised that you believe me so readily. Even eighty percent is awfully high when I haven't provided any proof.

[He shrugs, and continues walking down the path. No sense belaboring the point.]

It wasn't intentional, me telling Sharon who he was - is. [His mouth purses tightly at the slip.] I told her about L as a way of telling her about who I am, and that happened before he was brought here. I had no reason to expect he'd show up here.

[Mainly because L had been dead for years by Mello's perspective, which is a piece of information he elects not to share with Beyond for the moment.]

As for the reason I wanted to tell her who I am .... [His gaze drops to following his own feet as he takes steps forward.] I killed her. And I - I felt like I at least owed her an explanation as to why.

[Which is a testament to how strong of an influence Sorrow's resurrection had on him. Mello is not, generally speaking, someone who owes anyone anything.]