Apparently Lucas uses the branch of the world tree and smacks Claude with it on the head on Athy's 15th birthday, then Claude gains back his memories. I can't find a translation of the full novel, but I heard somewhere that Jeanette doesn't have a happy ending, so
That's not the end, but the latter half is a lot more lighthearted than I anticipated. So I think there won't be too many heartwrenching events, other than what happens to Jeanette, cuz I wanted her to be happy but I guess that's not possible.
Ah yes, also turns out that all 3 lives were her. She first lived as "Lovely Princess"'s Athanasia, reincarnated into modern lady, then went back to her first life to relive as Athy. Altho that was pretty obvious, it wasn't directly stated yet. She also ends up with Lucas and go official when she's 18, idk what happens to Ijekiel lmao
Anastacius (??) is also apparently the kid Lucas neglected way back then. Y'know, the ancient magic genius emperor occasionally mentioned. I thought it was kind of odd he's mentioned so often but now I see why ahaha. Anastacius died when Claude took the throne, but the ancient guy took over his body (not unlike Athanasia and Athanasia). From what I heard, he worked to become a magic genius because he wanted to prove to Lucas he was smart enough and a "worthy student," and this turned into sort of like an obsession. I'm guessing he messed around with black magic because of this obsession as well.
Anyway that's just what I've heard. I'm not sure if they're correct, just bits and pieces I picked up from various places. Also, this is according to the novel by Plutus. Spoon sometimes changes up parts of the story in the manhwa, so some parts might be different.