Call it a flashy billionaire's whimsy or a stroke of PR genius.

When Tesla Inc. CEO Elon Musk hinted on Twitter last week that a Japanese person could be the first tourist to go around the moon on board Space X's Big Falcon Rocket, social media began buzzing with speculation.

Names being bandied about included Takafumi Horie, the brash former president of Livedoor Co., and Daisuke Enomoto, another former Livedoor executive who came close to becoming a space tourist. But the consensus seemed to point to Yusaku Maezawa, the wine- and art-loving founder of Japan's largest fashion e-commerce company, Start Today Co., which operates the online apparel retailer Zozotown.