Crown prosecutor Nick Webby said just after 8am that day Yang had left home to catch a bus on Westgate Drive.
"She didn't realise it at the time – at least not until it was too late – that she was being followed that morning by the man that would kill her," he alleged.
The Crown alleges Li stabbed her 12 times across her head, neck, chest, stomach and arms with a hunting knife that had been purchased the day prior.
The blows sliced into a major artery in her neck and a major vein in her body, Webby said.
The court heard several members of the public - including a nearby construction worker - rushed to help Yang.
Webby alleged the construction worker had seen Yang tackled from behind and dragged to a grassy area before her assailant pulled her hair back to expose her face to the attack.
Another witness described a man punching a woman on the ground as she screamed hysterically, the prosecutor said.
Efforts were made to resuscitate Yang.
"Her life was unable to be saved," Webby said.
"She died not far from where she had been waiting for her bus."
As people had neared, Webby said, Li left in his car but was followed by a member of the public who managed to block him with his own vehicle.
Police arrived shortly after at 8.35am.
"Mr Li was arrested and taken into custody," Webby said.
"That arrest, or certainly part of it, was captured by the police Eagle helicopter which was hovering above the scene."
A bloodstained knife was found in Li's car, Webby said.
The prosecutor said before her death Yang had been frightened of the accused.
"She feared he would kill her if he knew where she lived."
Li had a tendency of breaching the protection orders that were in place, Webby said.
He had become "obsessed" with exacting revenge – or "justice as he viewed it" – after a property dispute in which the court ruled in her favour, he said.
The Crown's timeline
The court heard Yang and Li married in China in 1997 before moving in 2001 to New Zealand where they purchased a property in Blockhouse Bay.
Webby said that support worker described Li as "always wanting to bring the justice".
"To him his ex-wife did something wrong and didn't get punished for it."
Li told the support worker he was going to buy a big cleaver to chop off his ex-wife's hands and feet to make her suffer, Webby said.
Another protection order was granted in early 2018 and on February 9 the police removed a number of weapons from Li's home, including air-rifles and five crowbars, Webby said.
The Crown case would include that Li had been conducting some surveillance on his former partner in Massey, the court heard.
Yang reported seeing him loitering near her home on the evening of April 17, 2019, despite a protection order being in place.
"He shouldn't have known where she lived but somehow he did," Webby said.
The prosecutor said she told police: "I believe if Manchao knew where I lived he would kill me".
The following day police observed him in the area but he claimed he did not know where she lived and that he walked every evening on doctor's orders, Webby said.
He was given a warning, the court heard.
Webby said there were "strange goings-on" at another address in Massey in the months prior to Yang's death.
Tenants at her son's house reported "suspicious things" happening on the property starting on May 28, 2019, when they noticed all the tyres on their cars had been slashed.
Next a car was tagged with red paint before a dead rat and then a dead pigeon were found in the letterbox, Webby said.
Yang met with a community constable and advised that she suspected Li was responsible for the damage "as a way to get to her".
The trial will continue tomorrow with the first witness called to give evidence.
Domestic violence - do you need help?
If you're in danger now:
• Phone the police on 111 or ask neighbours of friends to ring for you. • Run outside and head for where there are other people. • Scream for help so that your neighbours can hear you. • Take the children with you. • Don't stop to get anything else. • If you are being abused, remember it's not your fault. Violence is never okay
• Shine, free national helpline 9am- 11pm every day - 0508 744 633 www.2shine.org.nz • Women's Refuge: Free national crisis line operates 24/7 - 0800 refuge or 0800 733 843 www.womensrefuge.org.nz • Shakti: Providing specialist cultural services for African, Asian and middle eastern women and their children. Crisis line 24/7 0800 742 584 • It's Not Ok: Information line 0800 456 450 www.areyouok.org.nz