Japanese e-commerce startup Mercari's Initial Public Offering (IPO) priced at $1.2 billion will make its 40-year-old Founder Shintaro Yamada a billionaire with about $1.04 billion fortune. Further, the indicated IPO price will give Mercari a market value of $3.6 billion. Founded in 2013, Mercari became Japan's first startup to become a unicorn at $1 billion or more valuation.