Rakuten, the Tokyo-based parent company of ebook vendor Kobo, is leading an investment round in the image-based social media website Pinterest, a move that could allow Kobo to expand its array of applications geared to “social reading.”

Rakuten is part of a group of companies that has invested $100 million in the online startup, which was launched in 2009 and, according to Reuters, now has about 20 million users. In turn, Kobo, which was acquired by Rakuten in January for $315 million, views the investment as an opportunity to enhance existing community functions, including its Reading Life app, which allows users to share comments via Facebook and Twitter.

We see amazing future opportunities with Kobo’s focus on social reading, Pinterest’s visual communication of things consumers love, and the e-commerce engine of Rakuten to one day create another avenue for consumers to engage online, says Kobo spokesperson Cerys Goodall in a press release.

Goodall adds: “We have seen first-hand the benefits of working with the Rakuten powerhouse and have taken advantage of their resources to expand internationally.

Since its takeover by Rakuten, Kobo has launched a bricks-and-mortar retail partnership in the Netherlands and expanded its retail operations in the U.S. and the U.K. It now claims to have readers in nearly 200 countries (which, in case you’re counting, would cover just about all of them).

Following Thursday’s announcement, Kobo director of merchandising Nathan Maharaj elaborated on what Rakuten’s investment in Pinterest might mean for the firm.

“We’re happy to feel like Pinterest is that much closer a member of our family,” he says. “It’s kind of like we’ve got a new cousin, and we’re just delighted.”

While it’s still too soon to say if Kobo will enter into a strategic partnership with Pinterest (similar to its relationship with Facebook), the ebook vendor’s aggressive approach to social-media marketing already appears to be paying off.

“What we know is that we’re seeing incredible growth in people posting their activity to Facebook using the timeline integration of our apps and devices to share what they’re reading, and when they’re reading, with their friends,” says Maharaj. “We’re seeing those events increasing, and we’re seeing them turning into interactive events where friends on Facebook are clicking those links and following it back through to Kobo, and closing that loop.”

Kobo already has a presence on Pinterest, and Maharaj says early experiments on the site have been promising. “I understand that ¦ ebooks maybe don’t strike you immediately as the most visual [media], but Pinterest is part of our social strategy,” he says. “A book cover is the visual hook for a book no matter what format you’re reading it in.”

Update: This story was updated with comments from Nathan Maharaj