Rebirth is the Creator's Spirit recognizing and unlocking the good within someone in United Universe's Timeline. A princess of light must show affection to someone before Rebirth commences, due to the affection that a princess of light shows leaving a certain mark on someone's soul. The Creator's Spirit uses that mark to choose the people/person he will Rebirth.
Rebirth is the main prerequisite to Super Sonic in United Universes, due to little or no chaos energy in that universe being the positive kind, and being reborn gives you the ability to convert that energy to positive chaos. Your spirit becomes more pure, and your acts become more sweet and kind, and if you have a significant other, you'll never leave them until they leave you. Bitter roots inside your heart will die, good hidden inside your heart will show.
Once you Rebirth for the 2nd time, the physical effects start to occur. Your strength becomes more than what Hyper Sonic can achieve, but only for 1 second.
When you are reborn for your 5th time, luck with follow you, as riches and sometimes, a beautiful maiden awaits you.
As more and more Rebirths occur, the effects start to be more pronounced, start to stack, and are longer. Once you hit your 8th time though, you cannot get any more of the luck or physical effects that manifest from Rebirth, but the purifying aspects still remain.
The only user of Rebirth is William John Red, due to a princess of light kissing him during Valentine's.
As the Creator wanted an easy way to figure out which were worthy of the power that Rebirth gives, a pure-hearted girl was born every century, telling them that they could give power to their significant other, if they so chose. The way the Creator said it made them afraid to corrupt their husbands, so they left them, dying alone in the process. The Creator decided not to tell the next pure-hearted girl their secret ability, knowing a great evil would befall the worlds soon. During the events of United Universes, Sophia Rose, a 13-year-old pure-hearted girl would catch the attention of a boy of the same age named William. She developed a liking for him, kissing William during Valentines. When he went to sleep, he woke up in Rebirth.
First, you must have been shown affection by a princess of light. That means she has recognized you as her prince, usually with a kiss that is meant to be romantic (That means if you are so happy, you kissed the bringer of that happiness, Rebirth doesn't happen). The next time you sleep, you'll have a dream of a man of light, speaking the words, "Awaken.". You'll feel as if your chest is filled with fire, waking up in a reborn state.
While going through Rebirth, the person's eyes glow a bright yellow, and a transparent yellow fire is seen emanating from their chests. As more Rebirths happen, the fire covers more and more of a person's body.