Hm? Isn't that an inconsistency in the plot? Or is the first part of this series included ...

There's no inconsistencies in the plot. This is a introduction flashback scene of Kyon's past where he remembers that he is under Edwin's servitude. As with what's updated on the site, he's a new character that readers have just learned about. The coming chapters will talk more on his role in the manhwa, so don't worry! :)