[The mention of the letters bring him back to where he was when he had written the second to final one and the moments thereafter, and he folds his hands together in his lap. The smile on his face - a young and healthy one - is peaceable in that distant sort of way that those who are touched by death often carry.]

Thank you for remembering. That alone means much to me.

[As for what he knows... After a pause in which he organizes his thoughts:]

I know of your mission. I also know of the many other realities that exist beyond my own. "The world where demons have overrun humanity", or "the world in which killing does not happen", of course - but also, "the world where Hijikata Toshizo fell to a strange illness", or "the world where Okita Souji has a precious subordinate named Kamiya Seizaburo". But even within a sea of difference, there are some things that remain the same. Almost like fixed points in the flow of time, which all else bends around to accommodate.