[This part is at least easy enough, because it feels more like a textbook lesson than an explanation of his background.]

Japan, or at least, the one I am familiar with, has something called a koseki. It is a document that traces lineage through several generations, a family registry. It is used for a number of things ...but it is a proof of your identity. Simply put, without it, you are not considered a Japanese citizen.

[His eyes trail down to his hands, and he keeps them there while he continues.]

Many years ago, my clan was driven beneath the ground by another, stronger clan. Exile was our punishment for being weak, and so beneath the ground we writhed like worms. Sometime after that the koseki was created... However ...b-because of our banishment, we were never registered. There is no koseki for the Ayase Clan. By ...all rights, we do not exist.