Rio and Allen, Allen and Rio. Those two names fit perfectly together like peanut butter and jelly or Princess Cadance and Shining Armor. In other words, they were the "match made in heaven". So that begs the question: when did this end, where did this go wrong?
Truthfully, he didn't know. If he'd known he had done something to hurt his princess' feelings, he would have apologized. On the other hand, it would have been a half-hearted apology as it was his nature.
She loved him with all of her being, even more than she loved her farm. She thought that all of this would stop once they exchanged their rings. Unfortunately, she was wrong.
He owned a shop and everyday the women of Echo Village came to him for all of their hair related needs. Everyday as he did their hair and listened to their problems or gossip he would casually flirt with them. It wasn't even only there where he would do it. Even if he was out with Rio, he would give subtle flirtatious remarks to his customers. Everyday she saw it and everyday it made her a little less confident in her abilities to make Allen truly happy with her.
She was beyond devastated when she finally chose to break it off. She couldn't do anything else but think about all those girls who Allen loved more than her.
He was absolutely broken afterwards. He began to ponder his mind just trying to figure out where he could have gone wrong.
She could only put it one way for him to understand.
"Certain mistakes I can forgive but some mistakes I can never forget."