HONOLULU, Hi. -- A former volleyball coach, who was charged with sex assault, made a deal with prosecutors.

Darin Yoshinaka will serve at most a year and a half in prison for having sex with an underaged student, officials said.

He was a 28-year-old volleyball coach at Maryknoll and his victim was a 13-year-old student there.

"I had sexual contact with her five times," Yoshinaka said.

Yoshinaka admitted he had sexual encounters with a 13-year-old female student pleading guilty to lesser charges under his plea agreement.

"Because he is guilty and it's the right thing to do," Yoshinaka's Attorney David Hayakawa said.

Prosecutors said they gave up a lot of potential prison time to assure a conviction.

"Criminal trials as we all know are not a sure thing a guilty plea assures a conviction," Prosecuting Attorney Scott Bell said.

Prosecutors and Judge Richard Pollack agreed that Yoshinaka's sentence would be five years probation. The judge can add jail time.

"Yoshinaka's plea agreement dramatically reduces the amount of his potential jail time down from 20 years to no more than 18 months," Bell said.

The prosecutor said the deal also spares the victim from having to testify publically.

"Something to be remembered is the perspective of the victim and her family. The prosecutor's office weighs that significantly in terms of any decision," Bell said.

Yoshinaka's hope is that the quick guilty plea will reduce his prison time.

"Nothing speaks stronger than standing up like a man and taking your punishment," Yoshinaka said.