They come to Sky's era, and overtime, Sky had built up the courage to finally propose to Sun!
He even collaborated with Four and Legend to make the ring themselves out of dusk relics. It turned out beautifully. He was so excited to do it, after all, it only made sense. They'd already waited so long to start dating, they knew each other inside and out already. Popping the question and taking the next step seemed like the right move to make.
So, he took her out on a date, on what he thought would be their last date unmarried.
They ate at the Lumpy Pumpkin, and then went flying through the clouds. He told her he had something he had been meaning to tell her. They landed on Skyloft.
He got down on one knee, and she started crying. But they weren't happy tears.
Before he could even ask, she said no.
Why? It made no sense, none at all. He stood up, confused.
Truth is, Sun couldn't stand seeing all his devotion, all his resentment. Everytime she looks into his eyes and sees all the pain he'd gone through for her sake, it feels like a knife stabbing her. She can see whenever he's on the verge of snapping, she can tell that underneath his kind smiles and soft looks, there's a deep anger he's buried, that's boiling and bubbling up.
She can't take it.
Neither can he, they've both just refused to acknowledge it. Because they're too afraid to.
They need to separate before they can come any closer.