I've read this manga called Sasurai Emanon (a.k.a. Emanon's Wanderings) about a girl who possesses all her ancestors' memories.
In some of the first few chapters a characters called Hikari made her appearance: she seems to be an acquaintance of the main character, but at a certain point (Chapter 7) there is this conversation:
It suggest that Hikari is some sort of time traveler, but it has never been explained and after this moment the character never appears in the story again.
The story seems to follow some series of novels: does the author explain something more about this character in these novels (or somewhere else)?