Media playback is unsupported on your device Media caption William Saito is on a mission to make Japan more entrepreneurial

When William Saito quit as a medical doctor immediately after qualifying, his parents refused to speak to him for two years.

But they're not complaining about the end result now, says the 44-year-old Japanese American.

He did the training to fulfil his parents' dream of him becoming a doctor, and as he jokes, his parents never actually said how long they wanted him to be a doctor for - just to be one.

The reason he left so soon was because he was determined to carry on the venture he'd begun at just 11-years-old while still in junior high school.

He had founded his own start-up company, which eventually focused on enhanced security for personal computers through technologies such as fingerprint and iris recognition.

Mr Saito formally incorporated the firm - I/O Software - in 1991 while he was at university. The company became a leader in biometrics and information security, and just 14 years later at the age of 33 he sold it to US giant Microsoft.

While the terms of the deal mean he can't reveal the price he received, Mr Saito admits he would have been in a position to retire then if he'd wanted to.

But unsurprisingly for someone so driven at such a young age, he has continued to work relentlessly, using his experience to help other entrepreneurs, particularly in his parents' home country of Japan.

Image copyright William Saito Image caption William Saito has always had his finger in several pies

While born and raised in the US, Mr Saito still believes he "owes the Japanese", because it's his heritage which he credits for his success. And now he believes he can give something back.

'Changed my life'

Mr Saito's parents couldn't speak English when they emigrated to the US, settling in Los Angeles in California, just two years before he was born in 1971.

Determined to give their son - the eldest of three - a competitive advantage to ensure he would thrive in their new country, they focused on mathematics, bringing over complex textbooks from Japan, and teaching him things well beyond the expected level for his age.

"That turned into a huge advantage for me," he says.

In fact, his maths became so advanced that his teacher ran out of suitable lessons, suggesting he played with "a thing called a personal computer" instead.

"I was able to take advantage of this lead and it changed my life," Mr Saito says.

Image copyright William Saito Image caption William Saito is particularly keen to support female Japanese entrepreneurs

On this teacher's advice, his parents took out a home loan to buy him his very own personal computer - worth about $5,000 (£3,200) in today's money - which from their point of view was aimed at helping him become a doctor.

But some work, organised by the same teacher, changed the direction of his life permanently. The teacher suggested to a friend - an accountant at investment bank Merrill Lynch - that Mr Saito, who at the time was just 10-years-old, could help with writing computer programmes.

"When I finished I received a cheque, and I didn't expect that.

"That really changed my view about doing something fun, but at the same time getting paid for it. It was definitely a wake-up moment for me," he says.

Despite his precocious start, Mr Saito denies that he was hot-housed, saying his parents exposed him to lots of different activities, and made it clear that success was about more than just good grades.

In particular, he says both the schools he went to, and his parents, emphasised the importance of volunteering.

It's a lesson he has taken to heart, and since the successful sale of his first firm, he has worked hard to support other would-be entrepreneurs.

He confesses one of his favourite pursuits, is judging business plans, and he travels globally to do this. To date, he calculates he's judged some 15,000 people in such competitions.

But his main focus is his parents' home country of Japan.

'Giving back'

In 2005, after selling I/O Software, he moved to Japan and founded venture capital firm and consultancy InTecur.

He also works as a special adviser for the Japanese government, specialising in cybersecurity.

But his main drive is to make the Japanese more entrepreneurial.

Image copyright William Saito Image caption William Saito's family always had high hopes for him

Image copyright William Saito Image caption As a child he was interested in many different things

As well as advising firms on various technology issues, InTecur aims to help young Japanese technology entrepreneurs become successful, something which he feels the Japanese culture, which typically bases seniority on age and experience, makes difficult.

"People in their 20s aren't given the opportunity. So for me I felt an obligation to give back to that next generation because I was given the opportunity," he says.

Image copyright William Saito Image caption His parents hoped he would become a medical doctor

Image copyright William Saito Image caption Mr Saito cannot reveal the price that Microsoft paid him for I/O Software

So far, the firm has invested in 24 companies, 14 of which are run by women - who he believes are also often overlooked in Japanese society.

He says he also makes a point of investing in people who have previously failed.

"Failure here [in Japan] is a bad word. I'm the reverse. You have to fail once and gain that experience first, then you know what your weaknesses and strengths are."

It is these attitudes, which he believes are stifling Japan's entrepreneurial spirit and making it harder for the country to grow.

But he's optimistic that things are changing. And it's this which makes him happiest.

"To unleash that potential and to see people make real change, I think I'm most proud about that.

"This is still an unfinished story but it's starting to take root," he says.

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