[He doesn't get all the context for it, obviously, but the visible reaction he gets is clear enough that this isn't an easy topic for him; so he can at least know that it isn't Aramis just bullshitting - not that he'd have expected that otherwise, despite his general cynicism at this age]
Yeah? [It's strange to think that someone could regret leaving him or find it difficult to do so, really, but... it's also a strangely reassuring thought, too, despite that hardship]