Former Maryknoll School athletic coach Darin Yoshinaka began serving an 18-month prison sentence this morning for sexually assaulting a seventh-grade girl on the school's intermediate volleyball team.

At the urging of the victim's mother, Circuit Judge Richard Pollack sentenced the 29-year-old defendant to the maximum time behind bars available under a plea agreement reached with city prosecutors.

"You are a predator and a pedophile," the mother told Yoshinaka.

The victim, who was 13 years old when Yoshinaka assaulted her, showed "an exceptional amount of strength and courage" in coming forward, her mother said.

"One of the first things she said to me was, 'Mom, I don't want this to happen to anyone else,'" the mother said.

Yoshinaka said, "I deeply want to apologize to (the victim) and her family. I take full responsibility for my actions."

His lawyer, David Hayakawa, asked Pollack to sentence Yoshinaka to six to nine months in prison, saying his client had no previous criminal record. Yoshinaka will undergo "an extremely extensive and strict" sex offender treatment program and will be a registered sex offender for the rest of his life, Hayakawa said.

"There is a very strong likelihood that he will not reoffend," the lawyer said.

Deputy Prosecuting Attorney Scott Bell asked Pollack for the full 18-month sentence, saying that his crimes had "calamitous consequences" for the victim and her family.

"No words of contrition can restore (the victim) to what she was before," Bell said.

Pollack commended the victim, who was present in court, for her bravery in coming forward and reporting what Yoshinaka had done.

The judge said he had received numerous letters of support from Yoshinaka's relatives and supporters but said the maximum allowable sentence was necessary.

"There is no question you had a devastating effect" on the victim, Pollack said.

Yoshinaka worked as an assistant volleyball coach at Maryknoll last year.

He befriended the victim and assaulted her in her home in November 2007 and again in January, according to court records.

The victim confided to a friend what had happened to her after the first assault and told her mother after the second incident.

Yoshinaka pleaded guilty in June to two counts of second-degree sex assault and seven third-degree counts of the same offense.

After completing his prison sentence, Yoshinaka must serve five years of probation, complete sex offender treatment and pay restitution to the victim and her family.

Reach Jim Dooley at jdooley@honoluluadvertiser.com or 525-8030.