Thousands of dollars worth of clothing and personal effects, passports and driving licences were taken.
Megumi Fujimoto said the theft saddened the women who had been looking forward to a fun-filled Northland break.
"I though 'Oh my God' when we saw it. This was our first day and we are very upset," Ms Fujimoto said.
The thieves took goods in a red North Face backpack, navy blue Nike carry bag and blue Chums bags. The women urged anybody with information to contact police. Less than a month ago two German tourists had their silver Toyota Liteace van broken into while at the Town Basin and their possessions rifled through and stolen. They lost air tickets, toiletries and a bag.
Whangarei district councillor Jeroen Jongejans, who is also chairman of the Northland Tourism Development Group and a member of the Tourism Industry Association board, said stealing from tourists was low and did enormous damage to the region, reputation-wise and financially.
The money the women would have spent on their trip would have employed somebody for about three weeks, but that would be lost.
"These sort of things can happen anywhere in the world and not just in Northland, but when it does happen it leaves a really bad impression.
"I feel so sorry for those women. Sadly there are some low-lifes in Northland who see other people's possessions as an opportunity. The cost to those people who get stolen from is great, but the costs in terms of our reputation as a visitor destination is huge."
Mr Jongejans said it was up to every Northlander to try to stop the problem by keeping an eye out and reporting suspicious people, vehicles or activities around tourist spots.
"We've got volunteers patrolling many of our carparks and visitors' places to try to prevent these things, but we can't be everywhere all the time," he said.
People could jot down registration numbers, makes and descriptions of suspicious vehicles and note suspicious people.
Anybody with information about the theft from the Japanese visitors, or any other crime, can contact Whangarei police on 4304500 or anonymously, and for free, via CrimeStoppers on 0800 555 111.