[That is not the reaction he expects. None of it is the reaction he expects, and if he were less of a shinobi he might have dropped looks-like-small-Itachi in surprise, but instead Sasuke yanks him closer to glare more closely into his face.

The details look right, but it's been so long that it would be embarrassingly easy to fool him on a purely visual level. It's the chakra that reads the same, if less ... precise, maybe, is the word to use.]

I am Uchiha Sasuke. Uchiha Itachi is my older brother. I don't know what I might be to you. [His eyes narrow, Sharingan spinning slowly: it's not an illusion, but ...] Who are you? What is your purpose?