Sadly, I can't tell you that bc Spoon isn't following the novel anymore ;-;
Athanasia was supposed to go to Atlanta and met Cabel, after that she would come back and the meeting was so sad.
According to the novel, it didn't take that long since Athanasia's comeback for Claude to get his memories back with the help of Lucas
Claude never got along with Jeanette/Zenit ;-; All of this was spoon's work
He is a character from beware of the brothers. Plutus's another work that is based on the country Atlanta, the place where Kiel went to study.
http://www.mangago.me/read-manga/beware_of_the_brothers/
Cabel is one of the brothers of this story. He fell in love with Athanasia and then they met in Obelia when Claude already got his memories back. Originally, he was supposed to be one of the Jeanette's harem but now he isn't.
I mean Spoon, the one who draw the manhwa, sometimes changes the plot, mostly the last chapters but she will continue with the novel. The worst is that she is taking so long with all of this, making Athanasia sad and Jeanette and Claude's relationship "good".
Originally, what took long was Athanasia's escape but not like the manhwa :/
Diana and Claude's story is so sad TT
when I read their story in the novel I cried a lot