Disclaimer: I don't own Harry or any other HP or TW character
Once Riddle was killed and Harry was finally free of having to always fight, he choose to leave. Leave the World that had been willing to let him die for there mistakes. Including his own mentor, a man he had trusted, mistakingly, for seven years. Even the Weasleys had betrayed him after he refused to be with Ginny. They had expected him to marry her like the good little boy he had been before he viewed his mentor talking about his necessary death.
Before he had become the Master of Death. Before he had lost the last of his innocence's by killing someone, even if Riddle couldn't really be regarded as human anymore. And before he realized that he really wasn't interested in her or any other female.
He had only ever been in one relationship, with Cedric. Which started in Third Year, after his one failed match. He'd woken up in the Infirmary in the middle of the night to see Cedric over him. He had been checking to see that he was okay after his fall. After that one thing led to another and he received his first kiss while in the Infirmary. They become a couple.
One that was swiftly added on to at the end of the year by Sirius. Who Harry fell for the moment he saw him, love at first sight, even while believing he'd betrayed his parents. Once Harry learned that Sirius was innocent, he was ecstatically happy. And he helped his love escape while also arranging a meeting.
A week later,Cedric met Sirius and fell for him to. Sirius told them that the were a bonded trinity, what muggles call soul-mates. Expect they were heart-mates to. Nothing would be able to separate them. Not even death for if one died both die. Harry was deliriously happy. For finally he had someone that was wholly his.
The three of them become lovers that night and thus become one together. They were joyously happy together for the next year, even with the Tournament. The came together almost nightly thanks to Cedric being a Prefect. So they were happy.
Until it all came crashing down around them with Cedric's death. Killed by Wormtail. Harry lived up to his title of Boy Who Lived and survived the impossible again. Living past his Bond-mates death. Sirius survived because of Harry. Harry's grief was profound and his power so vast he created a Miracle Child.
Miracle Children were extremely rare, the last known one being Merlin himself. They were created out of pure Love and Magic. Of grief so strong the witch or wizard needed a part of their lost love.
Harry's grief was so strong that he created Miracle Twins, something that had never been done before. A boy and girl. James Cedric Sirius Potter-Diggory-Black and Lillian Cassopedia Harriet. They were a part of all three of them.
Over the next year, Harry clung to Sirius desperately until he to was taken from him. And he once again survived it.And once again a Miracle Twins were born.Isabella Selena and Elena Catherine
After the death of his last Bond-mate, he gave up. Longing for death. Until Dumbledore came to him and convinced him to get vengeance. Which he became solely focused on, Riddle had to die. And he did.
Harry had rid the Wizarding World of their greatest mistake. And it only cost him his Bond-mates/his children's fathers, several friends, his backstabbing mentor and his innocence.
So Harry took his money, his children and his godson and left Britain forever. Completely unaware of what his life would become and completely uncaring.