When the Fuji Kindergarten in Tokyo was unveiled 12 years ago, the children spontaneously started running in circles, following the path of the oval-shaped, open-air roof deck.
It was a sight that brought tears to the adults, including Japanese architect Takaharu Tezuka, who designed the building.
"There was no instruction on what to do, the children just started running on the roof as if it were the most natural thing to do. The architecture, not humans, caused and enabled the movement of the kids," says the 55-year-old, who is married with a 16-year-old daughter and 14-year-old son.
At Fuji Kindergarten, located in the Tachikawa suburb in Tokyo, children run freely and climb trees that grow through doorless classrooms on the ground level.
The school, which has been billed the world's best kindergarten and was completed in 2007, adopts the Montessori educational approach, which encourages child-led play. It takes in kids aged from two to six.
Mr Tezuka spoke to The Straits Times last week when he was in Singapore as the keynote speaker for global furniture manufacturing company Steelcase's In The Creative Chair talk series. Held at Steelcase's WorkLife Centre in Mohamed Sultan Road, the invite-only talk series was hosted in Singapore for the first time, after previous editions in Beijing, Hong Kong and Tokyo.
Mr Tezuka founded Tokyo-based architecture firm Tezuka Architects with his wife Yui Tezuka, who is also an architect, in 1994 and is well-known for his simple yet highly functional designs that fulfil the needs of the users.
And people-centred designs never go out of style.
Ten years after it was completed, Fuji Kindergarten, which had clinched multiple architecture and design awards earlier, won the 2017 Moriyama RAIC International Prize.
The Canadian architecture awards recognise works of architecture that embrace humanistic values of social justice, respect, equality and inclusiveness within the community.
While his designs take inspiration from nature and feature strongly natural materials such as wood, Mr Tezuka says there is a deeper message he wants to send via his works.
For example, in 2012, he took up the massive task of reconstructing a kindergarten in the Miyagi prefecture that was destroyed in the 2011 tsunami. He used local historic timber trees that were destroyed by seawater to rebuild the Asahi Kindergarten close to its original location, but higher up on a hill.
Every structure in the building, from the floor to the handrail, was carved out of the mature trees and joined using traditional techniques, without a single piece of metal.
It was a project funded by the United Nations Children's Fund. The school reopened in 2012.
"Tsunami comes every 400 years so when it happens again, people will know where to find high ground. The timber will be saying to the children, 'In 2011, I was killed by the water but in 2411, be careful and come to me'," he says.
Even in clinical spaces, Mr Tezuka has found ways to inject nature.
In Okinawa, a women's infertility treatment clinic called Sora No Mori looks more like a resort than a medical clinic. Completed in 2014, the outdoor clinic is built primarily of wood and has lots of exposed corridors with natural ventilation and sunlight.
The medical care equipment is housed in curved rooms made with locally sourced Ryukyu limestone.
Because there is almost no natural forest remaining in Okinawa, the architecture firm had to revive the land, replanting indigenous vegetation and forests as part of the landscape.
The clinic won the 2015 Japan's Good Design Award and Japan Institute of Architects award.
His award-winning designs have inspired a number of copycats, Mr Tenaka says, but he is not offended. "We are still the original and, if people want the real thing, they come to us," he says.
His firm is now working on schools in India, Melbourne and Zhuhai, China.
But most importantly, Mr Tezuka wants his designs to be honest, authentic and to be of use. He says: "Architecture is not the same as an artwork. An artwork is pure creation and you can do whatever you want. Even if no one likes it, it's still art.
"But architecture, if nobody likes or uses it, it's pointless. It has to make sense for people to use."