Now that's a tricky question, because technically, Gilgamesh was dead. But on the other hand, technically, the fact that his soul was recorded in the Throne of Heroes meant that reincarnation ought to be impossible anyway.

Fortunately, Ritsuka knows better than to try to explain all of that. Instead, the concept of the Throne brings up a different important point.

"I don't think it's at the same time, exactly. Traveling between worlds and traveling through time are kind of similar, and there's no reason why times in completely different worlds should be the same anyway, right?"

Probably best not to ask right now why she's apparently familiar with time travel and parallel worlds.

"So even though I'd seen him not that long before I ended up here, in this world it just happens that his soul was reincarnated years ago."