Journey Into Classic Music
He had also been nameless until a woman working in the market gave him the name Ji Sung.
It was only when he was tracking his official record at the orphanage that he found his birth name Sung-Bong.
Choi's revelation came at age 12 when one night he heard a classical vocalist sing at a night club.
"All I had been listening to was loud nightclub music. But that song was so peaceful. It was the first time my heart felt strangely calm."
A few years later, he found Park Jung-So, a then-college student who posted an ad online for vocal training.
"I had no idea that people pay money for lessons," Choi smirked. He asked for free lessons.
Park said he was stunned by the bold approach.
"But no human would have asked this kid to pay for lessons after witnessing how he lived day by day," Park said.
Park started teaching basics of musical scales and codes from scratch and Choi reciprocated by doing chores.
To Park's surprise, Choi's learning curve took on an incredible speed.
"Yes, he had talent. But if you teach him one step, he would go day and night until he masters it. I think Sung-bong knew that he had to try ten times harder than the other kids," Park said.
Park also helped his determined apprentice who had always wished to attend something called school.
"I got into an art high school," Choi told judges during the pre-trial.
But that comment was deliberately deleted by the producers in the initial broadcasted version of the show, drawing doubts and sharp criticism of sensationalizing his story.
It turned out that Choi could not afford the extra fees required for lessons in school no matter how many part-time or overnight jobs he worked.
He ended up barely going to classes but the teachers gave him a graduate diploma anyway out of pity.
"He's got an incredible range of emotions. I mean who, how many of us have gone through what he's gone through?" said Kolleen Park, one of the three judges at the show. "Us as artists, we learn to express, search inside ourselves. Well he's got a whole basket full of ingredients, so much more than anybody else so he needs to learn the technique, really study hard, learn actually music and voice."
That's exactly what Choi is hoping for. But as of now, he is back to reality seeking once again a safe roof and a music master to teach the passion of his newfound life.
ABC News' Esther Kim and Yoon Gi Jang contributed to this article.