Police have charged a second man over "disturbing" claims he chained up a severely disabled girl and taunted her for his own "psychological satisfaction".
The girl was 15, with a developmental delay so severe she cannot speak, when her father and her mother's new boyfriend allegedly detained her at a home south of Wollongong in December 2018.
Police allege the men bound her hands in chain, covered her head with a sheet, positioned her on her knees and told her - amidst their laughter - "good girl".
The girl's older sister appealed for help as she filmed parts of the encounter on her mobile phone. "Please, if you're watching this, call someone," she is heard saying in one of three short recordings.
But the call for help only fell into police hands more than a year later, after the sister sold her phone to a stranger, who reported the matter.
Neither man can legally be identified, in order to protect the identity of the alleged child victim.
Her father was arrested in February and has been refused bail ever since.
Lake Illawarra detectives arrested the second man on Sunday afternoon.
On Monday, Wollongong Local Court court heard the girl had become frustrated and aggressive towards her older sister as a result of her condition, which can cause sensory overload and lead her to lash out at even slight changes to her surrounds.
With the girls' mother not home, the two men allegedly pulled the younger sister away and restrained her by wrapping chains around her wrists.
Police allege the mother's boyfriend kicked the phone from the concerned older girl's hand when she began filming.
He allegedly made threats when the sister warned that her boyfriend was on his way, telling her, "I'll make sure your boyfriend gets raped in jail" .
One video allegedly shows the man holding the chain over the kneeling girl as if she were a dog he was commanding to sit and stay.
In the final video, the girl is seen sitting on the lounge with both hands chained while her sister is heard saying, "oh my god."
The man faces a charge of detaining a person with intent to obtain an advantage. Police will allege the "advantage" was the psychlogical satisfaction of seeing the girl chained.
The court heard the man, aged in his late-30s, works full-time as a painter. He suffers a moderate intellectual disability and lives with his parents.
Prosecutor Leah Argent opposed bail in court on Monday, citing the strong prosecution case and seriousness of the allegations.
"It's my submission that these accusations were not only disturbing but cruel," she said.
"We wouldn't expect an animal to be treated in the way that this child was treated."
But Magistrate Jillian Kiely agreed to grant strict conditional bail, noting the man's significant cognitive impairment, limited criminal history and strong community ties.
Relatives shielded him as he departed the courthouse.
The matter returns to court July 29.