E-commerce startup Coupang, often described as the Amazon of South Korea, is said to be close to raising $1 billion in a private equity round led by Japan’s SoftBank Corp.

According to a report in the South Korean press (link in Korean,) the two parties are said to be in the process of due-diligence prior to the round, in which Softbank will take a 20 percent stake, closes.

The company will have a book valuation of $5 billion once the round closes.

Founded in 2010, Coupang offers a curated selection of diverse merchandise including baby goods, fashion, beauty products, consumables, home goods and decor, books and toys, sporting goods, electronics, and tickets for travel and cultural events.

Like Amazon, Coupang primarily ships products it stocks itself, and has built warehouses and a fleet of delivery trucks in what Forbes described as “allowing it to completely control the online retailing experience from the time a consumer browses for products to the point where goods arrive on their doorstep.”

The company claims to be the fastest-growing e-commerce site in the world and exceeded $1 billion in sales for the first time in 2013 and was said to be running at an annualized run rate of over $2.2 billion in December 2014.

Coupang’s mobile platform is said to be responsible for 80 percent of total traffic and 70 percent of revenue, with its app being download by 19 million mobile as of December 2014, one out of three people in South Korea.

For SoftBank, the investment follows in the footsteps of its previous highly successful investment in China’s Alibaba Group Holding Ltd., China’s answer to e-Bay.

Including the new round (once it clears) Coupang will have raised $1.4 billion. Previous investors include Illuminate Ventures, Cross Creek Advisors, LaunchTime, Rose Park Advisors, Greenoaks Capital Management and Sequoia Capital.