Well i haven't read the light novel but i am on the newest chapter of the manga
In my opinion after eris left i was thinking of different things that would happen when she comes back and meets rudeus here's the best one i made
After the events in the newest chapter of the manga Redeus sets out to find something or someone (idk) then while he's close to his goals he hears a voice that says "what do you think redeus is doing" he turns around to see a strand of red hair and a tail following that same person as he runs after that person, he grabs her and turns her around.
Eris: H-Hey what a-are you doi-
As Eris stares are his face wondering how he found her she says
Eris: H-hey long time no see, Looks like you read my note w-well I-i'll be off now
Redues: "Hey before you leave could I ask you a question and you too Ghislaine" with the eyes of a dead fish (ifykyk)
As redues asks his question his core was shaking, thoughts were running through his mind “why did you leave” i thought we were supposed to be together” all that time means nothing to you” and as Reudes aks his question he was thinking to himself that very same question
Redues: “i thought you loved me” as redues stares at her, a tear begins to fall down his face he couldn’t stop crying but the only thing he was doing was staring at her dead inside
Eris: “w-well i do bu-”
As reduce begins to speaks something cracks inside of him, as the crask continues something seeps out of that very same crack, a red substance, that was the rage&hatred he has stored since she left him
As Redues thought to himself to it felt like time stopped moving for everybody except him, before redues could say a word Ghislaine says “ let's talk in there” as she points to a bar they walk in together leaving to people who redues traveled with.
Ghislaine: hello Redues how ha-” before she finished she felt a ominous aura coming from redues
Redues: “was it funny”
Eris&Ghislaine: huh what do yo-”
Redues: was it funny leaving without speaking a word i bet it was, and i thought it was real
Eris: what do you mean the note says why i left
Redues: but you could've told me face to face before you left and it wouldn’t hurt as bad as it did
Eris: W-why are you acting like this, i have my reasons to leave
Redues: and what were those reasons, and i have something to share with you also
Eris: W-well the reason was to get stronge-” before she finished that sentence
Redues: for who? Huh
Eris: wdym it was for you
Redues: for me huh why
Eris: huh
Redues: why was it for M-E
Eris: because your younger than me and i have to pro-
Redues burst into laughter and yells “I DON’T NEED YOUR PROTECTION, all i wanted was to be with you but i was cast aside like a sip of paper”
Redues: I HAVE GONE THROUGH HELL AND BACK WITH YOU AND YOU LEAVE ME, I HAVE ONLY EVER FELT PAIN AND HEARTACHE SINCE YOU LEFT AND YOU EXPECT ME TO ACTUALLY LISTEN TO YOUR SAD STORY”
Ghislaine: chill out redues before i-
Redues looks at her dead in the eye and says “what are you gonna do, as you can see i’m not in the mood for holding back anything i’ll blow this place sky high and kill all of you if i have the chance NOW SIT BACK DOWN” s
Eris: where did i go wrong
Redues: you went wrong when both of you abandoned me
Redues sees something with his magical eye of eris slapping him, before she started it he blocks it and slaps her back
Eris stands there stunted by what just happened
Redues: oh so i see it was a lie every single thing we did together was a lie i’m leaving don’t ever contact me again or i’ll come for blood next time