Tupuhi fought her first match in 2008 and said people would often laugh because she was so small but, after she built up her confidence, she knew she could do it.
She says the preparation for the matches can be a struggle, helping the boxers relate more to the kids they are fighting for.
"There are times when you come away from sparring and you just want to cry because you don't think you're good enough."
A police colleague of Tupuhi's, Niwha Jones is also taking part.
Jones fights for the kids in a different way, running an after school programme to get Melville/Bader kids off the streets and doing something positive.
The programme, called Ara Tika, is a crime prevention initiative and is run by Jones separately from his police work.
"Initially I was working in one of the local intermediate schools with one of the at-risk youth and got quite a lot of interest [in the programme] so I moved it into the community.
"We were having a lot of crime and the behaviour of the kids after school wasn't very good so [it] just bridges that gap where they usually loiter around the shops and shoplift and tag and fight."
The classes are held at Richmond Park School in Melville and Jones has asked Te Wananga o Aotearoa to come of board with funding to give the kids a chance to compete this year, so they have the opportunity to work hard toward a goal.
Fight Against Child Cancer will feature 10 boxing matches, entertainment, competitions and prizes. It's on at the YMCA on February 1. VIP tablees of 10 can be booked by emailing battleforlife@hotmail.com; VIP tables $1200. Pre sales $25, door sales $34. Tickets from Hamilton i-Site office or at www.dashtickets.co.nz and on the door. Doors open at 6.30pm.