Collins had paid the fine because he accepted he had breached local regulations on carrying knives, he said.
But it was not a serious breach, and the size of the fine recognised his possession of the knives was "not accompanied by any sinister intent or intimidating purpose".
"And nobody was threatened or frightened."
Mr Castle said the circumstances with the Brazilian gang had played a part in Collins' release.
"All that information of course was provided to the police, there's been a thorough investigation."
Mr Castle said his client would love to play rugby again.
"He's still in the prime of his fitness."
Arrangements for Collins' return to New Zealand were still being made.
Collins' father Frankie Collins last night told the Herald his son would return to New Zealand but was yet to speak to him to confirm details.
"He's going to be arriving in New Zealand (his) lawyer said, and that's what we are waiting for, him to get home," he said.
He looked forward to speaking with his son and was relieved to hear of his release.
"I am, I'm very very happy."
Mr Collins was in the dark about what had gone on in Japan.
"We just have to find out the real story or what was happening. At the moment I don't know what has been happening."
Frankie Collins had heard media reports of his son's fears that a gang of Brazilians were targeting him but didn't know what to make of it until he had spoken with his son.
Collins, 32, told TV3's John Campbell this week that he had a "misunderstanding" with a gang in Japan.
He believed he was being followed on the day of the incident, resulting in his walking behind a counter at the upmarket store and taking out a knife in front of frightened staff. Collins said he believed he wouldn't be attacked around so many people.
Rumours he was on drugs were not true and all tests had come back negative. He said he was treated "very kindly and very generously" in prison.
A Ministry of Foreign Affairs spokesman confirmed the consul from the New Zealand Embassy in Tokyo had been involved in Collins' case over the past week.
He could not comment on whether Collins would have to leave Japan as part of his release.
* Read the Herald's live news blog here.