Japanese billionaire Yusaku Maezawa, who blasts off for the International Space Station this week, is an irreverent space enthusiast who has made headlines for splashing the cash on modern art.

The 46-year-old tycoon is the founder of Japan's largest online fashion mall and is the country's 30th-richest person, according to business magazine Forbes.

But he is far from the traditional image of a staid Japanese businessman, with more than 10 million people following his Twitter account, its handle a play on his first name: @yousuck2020.

And he's a big spender, particularly when it comes to his twin passions: modern art and space travel.

He hit the headlines in 2017 when he forked out a whopping $110.5 million for Jean-Michel Basquiat's 1982 painting "Untitled", a skull-like head in oil-stick, acrylic and spray paint on a giant canvas.

It was a record price, but Maezawa insists he is just an "ordinary collector" who buys pieces "simply because they are beautiful".

On December 8, Maezawa will become the first space tourist to travel to the ISS with Russia's space agency Roscosmos since Canadian Guy Laliberte, co-founder of Cirque du Soleil, in 2009.

He will be accompanied on the 12-day mission by his assistant Yozo Hirano, a film producer who will be documenting the journey for Maezawa's YouTube channel and its 754,000 subscribers.

How much Maezawa has spent on his upcoming space adventure is unclear, as the price tag has been kept a secret, though similar trips have cost millions of dollars.

But the cost is unlikely to make much of a dent in the $1.9 billion net worth Maezawa is estimated to have accumulated through his firm Zozo, previously known as Start Today, which operates the hugely popular ZOZOTOWN online fashion site.

Maezawa arrived in Kazakhstan for space training in November, and has said he is "not afraid or worried" about the voyage.

Japanese billionaire Yusaku Maezawa will blast off for the ISS as part of a 12-day mission Japanese billionaire Yusaku Maezawa will blast off for the ISS as part of a 12-day mission Photo: POOL via AFP / SHAMIL ZHUMATOV

He has been soliciting ideas for things he should do in space and asking questions including: "Do you move forward when you fart in space? What happens when you play Pok?mon GO in space?"

In Japan, Maezawa's exploits are often fodder for gossip magazines, with a particular focus on his love life over his space exploits.

The ISS trip won't be Maezawa's last space odyssey, as the businessman has also booked out an entire SpaceX rocket for a trip around the Moon scheduled for 2023 at the earliest.

Maezawa originally said he planned to invite six to eight artists on the trip, asking them to create "masterpieces (that) will inspire the dreamer within all of us".

But in March, he announced he was broadening the search beyond artists, and claims to have received one million applications for eight spots on the rocket made by Elon Musk's firm.

Maezawa has made a habit of holding online competitions, creating a Twitter frenzy in 2020 when he said he would give away $9 million to 1,000 people as a "social experiment".

But he backed out of a separate competition seeking candidates to be his girlfriend... after attracting nearly 30,000 applicants.

As a young man, Maezawa had aspirations in the music world and was a drummer with a band named Switch Style, which made its debut in 2000.

But he came to feel the business world was more creative than music, and has said writing and performing eventually become a frustrating routine.

He began dabbling in business even before the band's debut, and has attributed Zozo's success to the fact he and his staff were "doing what we enjoy".

"Work hard, make people happy, earn money, buy big dreams, visit amazing places, meet people, experience great things, grow as a person, and work again," he wrote in May on his Twitter account, explaining his philosophy.

"The cycle repeats. The cycle of making dreams come true. We can even go to space."