A violin teacher who was charged for allegedly indecently assaulting a six-year-old girl over a period of several months was refused bail in court today.

Oscar Ahn, 21, was employed by a day care centre to teach young children how to play the instrument when it is alleged that he carried out blatantly predatory behaviour.

The teacher was charged with 20 counts of indecent assault of a person under the age of 16 after being accused of touching the young girl’s leg and bottom with his groin on a weekly basis, for months.

Violin teacher Oscar Ahn was charged with 20 counts of indecent assault of a minor and refused bail in court today. Picture: Supplied. (9NEWS)

A Sydney court today heard Ahn’s alleged offending was uncovered during an altercation with the girl’s parents at a Costco outlet.

When the girl’s mother told her to say hello to Ahn, she “drew back towards her mother like she was frightened,” and said “he touched me,” court documents revealed.

The 21-year-old then confessed his guilt in a series of text messages to the girl’s father.

“I didn’t think about how a child would feel, how scared they would have been and must have been so frightened to come to the lesson,” the messages said.

“I really feel that my actions were very wrong and I regret it so much.”

After handing himself in at Redfern Police Station yesterday, the court today heard that Ahn admitted to officers interviewing him that if the Costco altercation had not happened, his alleged offending would not have stopped.

The teacher allegedly touched the young girl's leg and bottom with his groin on a weekly basis. Picture: Supplied. (9NEWS)

Ahn’s father, who attended today’s hearing and planned to take him back to Victoria with him to see a psychologist, made no comment outside court on the matter.

Greg Meakin, Ahn’s lawyer, said it was disappointing that he was refused bail.

“I’m always disappointed when a client who is deserving of bail, doesn’t get bail,” he said.