Japanese eCommerce leader, Rakuten, owner of e-reader company Kobo, said it plans to invest $100 million in the trendy social media site, Pinterest.

Pinterest, which allows users to 'pin' images and follow other people's images in an online scrapbook framework, is enjoying a tremendous surge in popularity having leaped from less than one million users in May 2011 to more than 20 million today, according to comScore.

Rakuten, which acquired Toronto-headquartered Kobo in January for $315 million USD, plans to expand Pinterest into Japan and its 17 other international markets. That task is made considerably easier in light of the eCommerce giant's ownership of online retailers Play.com in the UK, Buy.com in the US, Priceminister in France, Ikeda in Brazil and Tradoria in Germany.

"While some may see e-Commerce as a straightforward vending machine-like experience, we believe it is a living process where both retailers and consumers can communicate, discover, and curate to make the experience more entertaining," said Rakuten's chief executive, Hiroshi Mikitani.

Rakuten reports that existing shareholders Andreessen Horowitz, Bessemer Venture Partners, FirstMark Capital and other angel investors helped to raise the $100 million capital.

According to The Wall Street Journal, the investment deal places a $1.5 billion valuation on Pinterest.

Discuss Rakuten's deal further in our e-reader forum .