[Even as Shiro offers to try, he kind of realizes he's not all that invested in the explanation either. Not for the "impostor" or the real Shiro or whoever this one in front of him now is. When he steps closer, Keith stays put but his shoulders square defensively again, ready to step back. That should be his instinct anyway, but it feels - off, deep down.]
-- I'm fine. [Very clearly not, not feeling it mentally either tbh, but being stubborn about this is still his specialty, maybe now more so when he doesn't know what the hell to trust.]