The story is currently locked while I revise it. (I suddenly realized that my plot was almost a complete mess, so I'm going to rework it from the beginning and reread the original. You can find me on Weibo: It's Acile. Fellow fans are welcome to come chat about the plot.)
In a nutshell: Arnold swears revenge after being tricked by Byakuran when he was young.
Literary version
He stood atop a field of ruins, gazing into the distance. The prosperity of the past was long gone. This was both the beginning of everything and its end.
May our friendship last forever.
Silly version
The Vongola are at it again, causing chaos! The Guardians are tearing down the castle again!
The innocent bystanders are beside themselves with despair.
Giotto holds a report on the budget deficit and resolves to learn from his mistakes. He is absolutely going to find some unlucky soul to share the burden.
Giotto (with the Sun's smile): Would you like to join the Vongola, Arnold?
Arnold (taking a step back): ...I refuse.
Serious version
This is a story that begins in summer and will also end in summer. No matter how treacherous the journey, the summer sun will eventually dispel every shadow.
May our friendship endure.
GIOTTO (holding out his hand): Whatever you choose, you will always have my trust. No reason or words are needed. After all, we're comrades, aren't we?
Damon Spade (folding his arms and raising an eyebrow): What exactly are you after? Nufufu, you're making me feel a thrill I haven't felt in ages. I can't wait to discover the truth about you.
Come to think of it, how about working with me? We might get along quite well.
G: To be honest, I still can't trust you. But please let me apologize for doubting you before.
You were right.
Lampo (turning away and taking out a piece of candy): Well, I'm a man who knows how to separate business from personal matters, so I'll grudgingly approve of you. You can come to me if you need anything, of course, except when it comes to that Damon Spade guy.
Elena: Damon is actually a very sensitive person. If you can, please help him when he starts down the wrong path. At the very least, don't let him keep making the same mistake.
Knuckle (clenching his fist): His personality is awful, but he might turn out to be a pretty decent guy after all.
Asari Ugetsu (swinging his long sword): Come now, don't be so cold. We're comrades, after all. Let's fight side by side.
Arnold: ...What a troublesome bunch. Especially you, GIOTTO. Don't come looking for me unless you have a reason.
Timeline: First Generation Arc → Tenth Generation Arc → Future Arc → Tenth Generation Arc → First Generation Arc (mainly the First Generation Arc, with very little interaction with the Tenth Generation characters)
Theme: Serious drama