[The fact that Shun almost physically recoils at that suggestion probably says all that really needs to be said about it, and he holds up a hand as soon as she starts trying to figure her way through her phone.]

I don't like having my photo taken. And I'd rather not think about old times that much. [It usually just means unnecessary pain, and he has plenty enough of that in his life already.] There's a reason I suggested anyone other than me.

[He can think of several people off the top of his head who'd give Mabel the picture she wants, but he's not one of them. The single person here who has any photos of him is also by far the person he's closest to, so there's a high bar set.]