"There's a really cool online platform called Bridge which has modules to fill out in between those Zoom calls.
"That means we can discuss those topics during the call, instead of spending that time learning about them."
The online modules cover topics such as stereotypes, empathy, dealing with conflict and resilience.
Donson said the first forum involved students working through "metaphors of culture".
"That was all about the visible and invisible side of it," Donson said.
"You see the way a culture greets each other or the way they dress, but then there are things like relationships, gender roles, and health.
"One diagram we used was the iceberg, with those visible aspects being above the water and the big chunk of ice underneath being the invisible side of a culture."
New Zealand's favourite spread was something that needed explaining to their Japanese colleagues, Donson said.
"There was a slideshow with jandals, sheep and Marmite," Donson said.
"When their facilitator asked them what they thought Marmite was they were like 'medicine?'.
"Nope, it's definitely not."
Palmer said the other metaphor assignment they tackled involved identity.
"That used a flower, with all the petals representing our identity - race, religion, gender, sexuality, profession, health, all that sort of thing.
"Then we brought them to the lesson and discussed them in our little groups, which was really good."
Part of Girls College's goal was to give students "a holistic approach to life", and an initiative like the Global Competence Certificate had the school's full support, Principal Sharon Steer said.
"It makes me immensely proud to see how deeply the girls are thinking about complex issues," Steer said.
"They are only 16 years old.
"Of course there's a certificate at the end of it, but it's also about showing an interest in and caring about other people, and that's exactly what they are doing."
As well as New Zealand and Japan, modules will be delivered to international learners from India, China, Vietnam, Thailand, the Republic of Korea, Indonesia, Brazil, Mexico, Colombia, Peru and Chile.
Locally, students at Whanganui High School and Cullinane College are also taking part in the exchange.