Passers-by stop and stare at the ramshackle, hand-built concrete tower that looks like it has been lifted right out of a Japanese animation and dropped onto a real-life Tokyo street.
Its creator, who spent almost 20 years making the distinctive four-storey Arimaston Building, thinks his slow approach to construction can be an example to the world.
"It used to be that there weren't enough things in the world, but now there are too many," 59-year-old Keisuke Oka told AFP inside the building's curved grey walls.
"We need to stop mass-producing things and find another way, otherwise we'll be in trouble."
With its wobbly lines and weird, wonderful ornamentation, Oka's building has been compared to the animated Studio Ghibli movie "Howl's Moving Castle".
The architect himself has been dubbed the Gaudi of Mita, referencing the famed Spanish architect and the Tokyo area where Arimaston Building is located.
Inspired by Japan's avant-garde butoh dance, Oka made up the design as he went along.
Growing up, he felt buildings in Japan's towns and cities looked "very sad and devoid of life", as if they were "all designed on a computer".
"The person who constructs a building and the person who designs a building are very far apart," he said.
"In order to give the building some life, I thought I would try to think and build together at the same time."
Oka started construction in 2005. Apart from the help of a few friends, he made the entire building himself by hand.
He claims the concrete -- which he mixed himself -- is of such high quality that it will last for over 200 years.
Oka says the structure is basically finished. He plans to live in the top three storeys and use the ground and basement floors as a studio and exhibition space.
When he started, he had no idea the project would take almost two decades.
"I thought with the ability I had, I could do it in three years," he said, explaining that the improvised nature of his design brought constant challenges.
Oka grew up in rural Japan and was an exceptional architecture student who was told by his teachers he would go a long way.
He suffered a physical breakdown in his 30s and gave up architecture for a while, before his wife persuaded him to buy a small plot and build a house.
He says making Arimaston Building has restored his confidence, and he enjoys the amazed reaction of people walking past.
"It's very easy to understand the contrast with the high-rise buildings right behind it," he said.
"I think there is some value that the city can take from it."
Arimaston Building stands alone on a sloped street, making it all the more striking.
The area is undergoing large-scale redevelopment, and the apartments that once stood next door have been demolished.
As part of the changes, Oka's building is scheduled to be moved 10 metres backwards in a process that involves transporting the entire structure on rails.
Once that is complete, he intends to move in and continue working on the finishing touches, alongside his university teaching jobs.
Amid all the upheaval in the area, Oka hopes people will be able to see the value of making something by hand.
He says he was inspired by his upbringing, when his mother made clothes for the family because they couldn't afford to buy them.
"More than half of the clothes we make now, we throw away, he said, describing a world "overflowing with things".
"We need to start making things at a slower pace," Oka said.
