Quy Huy Hoang is accused of sexually abusing four girls while tutoring them in their southwest Sydney homes between May 2011 and July 2014.
Assisted by a Vietnamese interpreter, the 76-year-old pleaded not guilty to four counts of sexual intercourse with a child under 10 and four counts of indecent assault of a child under 16 at Sydney's Downing Centre District Court on Thursday.
Hoang abused the trust that three families had placed in him to teach their daughters, crown prosecutor Alex Morris during openings in the judge-alone trial.
Between May 2011 and March 2013, he allegedly molested two sisters, one of whom was aged between three and five years old and the other between six and seven.
After experiencing multiple family tragedies, the girls' mother received a call saying Hoang heard of their plight and wanted to help.
He tutored the sisters free of charge, initially teaching the girls in the dining room but then persuading their mother it would be quieter in the toy room of their home.
"The reason Mr Hoang suggested this was because he wanted the privacy of another room to provide him with the opportunity to sexually offend," Mr Morris told Judge Penelope Hock.
The tutor is accused of taking cream from a black briefcase and using it to digitally penetrate one of the sisters.
On the same occasion, he kissed the girl on the lips and made her "pinkie promise" not to tell her mother, Mr Morris said.
That girl was separately forced into touching the tutor's genitalia, the court was told.
Her sister was assaulted when Hoang touched her sexually through her pyjamas, the prosecutor said.
After the girls' mother reported the matter to police, the tutor was arrested at a Catholic church service in August 2014.
During a search of his home, police found a black briefcase filled with maths worksheets as well as vaseline, creams and lip-balm.
One of the lip-balm containers contained a substance chemically identical to KY Jelly personal lubricant, Mr Morris said.
On his mobile phone, police found a number of photographs of children, including the four alleged victims.
Hoang is accused of sexually assaulting another girl and her school friend, both aged seven years at the time, between March and July 2014.
He convinced the mother of one of the girls to tutor them in her son's bedroom, getting her to install a door lock and blackout curtains in the room.
Hoang allegedly forced one girl to touch his penis and digitally penetrated her.
He touched the other girl on the outside of her pants and digitally penetrated her, causing her to burst into tears, Mr Morris said.
"I don't want to do it, I don't want to be here," the girl allegedly said when her mother asked what was wrong.
The trial continues on Friday.
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National Sexual Abuse and Redress Support Service 1800 211 028
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