During his opening address, Crown prosecutor Greg Hollister-Jones told the jury that Neketai was charged as the principal offender.
He is accused of punching Mr Kimura so hard he fell backwards, hitting his head on the concrete driveway before kicking him in the face, causing massive head injuries.
Mr Kimura was found lying face down on the concrete at the bottom of some steps in a pool of blood by his widow, Rosina Kimura.
His injuries included a fracture to the left side of his head which extended to his left eye socket, also extensive bruising and swelling to his face, the court was told.
Mr Hollister-Jones said Mr Kimura underwent surgery, but died six weeks later.
The Crown case also relies on text message exchanges between all four co-accused between September and October 2011, DNA evidence, including blood found on Neketai's shoes, and CCTV footage of the accused's movements before and after the attack.
"Text messages show that Neketai went to the home to collect a debt of more then $30,000, and Hiku, who was there, was to assist him as back up,'' Mr Hollister-Jones said.
Mr Hollister-Jones said Hiku lured Mr Kimura out of the house without raising suspicion by being friendly to the deceased's daughter, Melani, who had answered the door.
A series of text messages on October 5, 2011, included one from Rewiri who, although in prison on the relevant dates on an unrelated charge, had encouraged Neketai to carry out the attack, he said.
Mr Hollister-Jones said in one text exchange Neketai described Hartley as "his prospect''.
Mrs Kimura gave evidence that after her husband went down to the answer the door and didn't return she looked out the window and saw a strange car parked in their driveway.
"I saw a young fella sitting inside and another couple of men standing at the bottom of the front door steps.
"I never thought anything about it and then after a few minutes I heard a loud bang and just thought it was the front door banging and waited for Gary to come back up but he never did.
"When I looked down from the dining room window I saw Gary lying on the concrete driveway, he was lying face down in a pool of blood which was all around his head ... I screamed and ran down to help him.''
Mrs Kimura said she reached her husband, who at one stage attempted to get up, and lunged at her in his semi-conscious state. As she was struggling to hold him down, he fell again hitting his head on a concrete wall, and they both landed on the concrete driveway, where he lay choking on the blood pouring from him, and struggling to breathe.
She whacked him on back trying to help him breathe but he eventually lapsed into unconsciousness.
A neighbour arrived and gave Mr Kimura CPR and Mrs Kimura said she then "waited and waited" for the ambulance to arrive.
The trial is set to take seven days. It continues today.
