After much blood, sweat and tears, a Tauranga teen has grabbed the ultimate title in learning the art of karate.

After a gruelling 18-hour overnight test, 13-year-old Chase Marshall achieved what he's been working towards for six years – his black belt in karate.

The grading test, known as the toughest black belt grading in New Zealand, was the culmination of almost half a lifetime of hard work for the ACG Tauranga student.

Chase, who was one of six candidates to receive their first-degree black belt at the grading this month, had already undergone an intensive eight-week-long pre-grading training programme through Mile High Karate.

He endured a trial that would challenge the most seasoned athlete. Starting at 6pm on a Friday, Chase and his fellow black belt candidates worked through the night doing kata (forms), free-fighting and fitness tests – including running up Mauao to see the sunrise.

After a sleepless night, at 10am they performed their final kata at the QEII Centre in front of an audience and were finally awarded their belts.

Chase has been attending Mile High Karate since he was seven years old, and has had the black belt in his sights for the last two years.

'The hardest thing about the overnight test was just keeping going, but I was really focused on getting my black belt, and my mentors and instructors really helped me get through it,” says Chase.

His mother Kay Spencer says learning karate has been hugely beneficial for her son.

'It's hard for kids these days to find really good role models. Here they are surrounded by guys who can break bricks with their bare hands, but are considerate, supportive and empathetic,” says Kay.

'It's not just about karate – it's about discipline, and having somewhere to be physical, and blow off steam in a really positive way.”