There was a little-known fact that Reborn was in fact a sky, so when he's introduced to the Acrobaleno as a sun (his secondary) things get a little confusing.
Reborn stared at the sunny yellow pacifier around his neck with confusion of course it didn't show on his face. 'Sun? But I'm a sky.... then is the sky pacifier bloodlocked?' A look to the side at a picture of the previous Acrobaleno answered that question. The sky in the picture was nearly identical to the current one. He decided to say nothing even as Fon, his only element, looked at him confusedly. A minute gesture answered Fon's unspoken question as they gathered with others.
Reborn thought back to how Fon became his guardian, when this whole Arcobaleno business started.
Flashback
It was just a few days after they were gathered as the world's strongest in there respective talents. Of course it went unnoticed that there was only 7 of them instead of the several hundred some would think when thinking of the many talents in the world. But the thought never crossed anyone's mind as all they knew was that they were called for a job and these were their coworkers no matter how stupid or civilian they were.
Anyway it was just a normal day for the sky not looking for guardians Reborn, who was relaxing in his hammock without a care in the world when a weight made itself known on his chest. Opening his eyes he spotted the languid Fon getting comfortable on top of him. They blink briefly when their flames moved into sudden instantaneous harmony. Deciding to not question their flames they got comfortable.
"So why did you suddenly decide to sleep with me?" Reborn asked.
"I tend to stick around the strongest in the room other than me, so I don't get caught of guard. However I wasn't expecting that to happen." Fon replied honestly.
"I didn't either." They left it at that.
End Flashback
Nothing really changed after that as no one noticed how Fon always seemed to defer to Reborn.
"Luce what's the meaning of this!?" Reborn's train of thought was interrupted by Skull's uncharacteristic shout. The cloud look absolutely outraged the kind you see when a cloud is about to let lose all it's rage and hate onto the closest victim.
AN: And just to be a troll I'll end it here cause the rest I feel will spoil too much.