The teenager has been remanded in custody of Oranga Tamariki to re-appear in the Whangārei High Court for a case review on April 22, 2021.
The stabbing occurred at the corner of Paihia Rd/State Highway 11 and Waimangaro Rd in Opua, about 200m north of the Roadrunner Tavern.
Northland police recently appealed for witnesses who witnessed an altercation before Willems' death.
A woman who witnessed an altercation outside the Work and Income building in Kawakawa's main street had spoken with police, but Detective Senior Sergeant Geoff McCarthy said it was believed there had been a further incident that night.
The inquiry team wanted to hear from anyone who witnessed an altercation in the bus bay at Bay of Islands College, on the corner of Derrick Rd and North Rd, in Kawakawa between 10.10pm and 11pm on Thursday, January 7.
"There would have been a group of up to five people, and they may have been making considerable noise," McCarthy said.
Anyone who witnessed the altercation, or saw a silver Toyota Altezza car, registration MQE620, in the Kawakawa/Opua/Kerikeri areas late on Thursday night and into Friday, was asked to contact the police on 105, quoting file number 210-108/7855.
Anyone with photos or videos that might assist was asked to upload them to the online portal https://crew.nzpolice.org.