TOKYO, JAPAN - Kikuo Ibe walks into the conference room at the Casio R&D facility in Hamura, West Tokyo, with a fuschia paper heart pinned to his chest.

"This is my heart. I want you to know how happy I am that you are here," he says.

It is hard not to warm up to the dimunitive 67-year-old with the kindly demeanour, John Lennon glasses and zany sense of humour.

For someone regarded as one of the most important figures in modern watchmaking, his humility is also extremely refreshing.

Ibe is the man behind the Casio G-Shock, the iconic line of almost indestructible watches. Since it was launched more than 35 years ago, more than 100 million of these hardy timepieces have been sold.

How Ibe invented the G-Shock (an abbreviation for gravitational shock) makes for a darn good yarn.

When he graduated from high school, his father gave him a mechanical watch - one he loved and treasured. One day, someone accidentally knocked it off his wrist and it broke into pieces.

Upset, the mechanical engineering graduate from Sophia University decided to invent a rugged watch which could take a great deal of abuse.

His target? A watch with a battery life of 10 years, is water resistant to 10m and could survive a fall of 10 feet.

Then working in the digital watch design department of Casio, he beavered over this project outside office hours. From the third-floor men's toilet of Casio's facility in Hamura, he would drop prototypes. Countless broke but he would tell himself: "Never give up."

Ibe's work eventually gained enough traction for his employers to make it an official project, and assign him three assistants whom he called Team Tough.

They went through 200 prototypes, but a breakthrough eluded them until one day when Ibe spotted a girl bouncing a ball in a park.

Eureka! He decided to put the watch's movement inside a "floating module", which would isolate it from shock.

In 1983, the first G-Shock model DW-5000 was released with 200m water resistance and the ability to survive a fall of more than 10m. Since then, there have been hundreds of iterations, with prices starting from $120.

The latest is the Casio G-Shock G-D5000-9, fashioned from 18k gold. Only 35 pieces of this model, priced at a whopping $100,000, are available worldwide.

Having the G-Shock become a global phenomenon was something he did not expect.

"I actually designed it for construction workers and those in tough jobs. I was surprised we managed to capture such a big audience," he says through an interpreter.

"During the development stage, we thought: 'This watch doesn't need repairs so a lot of repair shops may be out of jobs.'"

"But what is interesting is that it has attracted a lot of collectors. They buy more than one G-Shock and that thankfully has allowed us to maintain the growth of the G-Shock business today."

Over the decades, he has met more than his share of rabid G-Shock fans.

"One day, I met a mother with a one-year-old baby in her arms. She told me: 'We're both big G-Shock fans.' I can understand the mother being a fan but a one-year-old infant?"

"She then told me that when the baby was teething, he loved biting on G-Shocks because they helped soothe his discomfort."

Surprisingly, Ibe himself has only three G-Shocks - all classic DW-5600 models."I've had them for more than 20 years. One black, one white and one red. The black one I wear during spring and autumn, the white for summer and the red for winter."

For the man behind such a high-tech watch, he is surprising in other ways.

"I don't use a smartphone, I don't look to technology for inspiration. I see more appeal in the analogue world," he says.

Many of his ideas come to him while he is doing what he loves best: growing vegetables.

"When you grow vegetables, you see everything, from the sprouting to the harvesting. The analogue world and my hobby often come together and give me ideas. When I die, I'd like someone to dissect my brain to see what's going on in there."

He loves to "practise predicting things", he says.

"We're looking at space travel in the near future. In space, conditions are extreme, with extremely high or low temperatures. If I'm alive to see it happen, I'd like to create a G-Shock which can withstand these conditions in space," he says.

"It will be a watch that my alien friend Taro can wear too," he adds cheekily.

Asked if the mantle of G-Shock inventor carries great pressure, he replies with a grin: "I'm quite dense and pressure-resistant. The people around me have pressure about what next to do with the G-Shock. Not me. I am okay."

Since its debut, the watch has evolved and spawned many iterations.

"We have new teams of young people with their own creations and ideas. I don't have a say in everything. If I wanted to do my own G-Shock, I need to get my own team."

Have there been any models which had him furrowing his brows?

"When they first told me about the idea of a gold G-Shock, I thought that it was not quite a G-Shock thing. But when I saw the final product, I was so impressed and thankful."

So he never gives up, just like his mantra?

"It's something I say to myself because I keep giving up," he quips.

"I've been working on a project to create an all-sapphire G-Shock but we're at the stage of admitting that it is almost impossible."

"But I don't know when I should give up."