Ben Anderson is amateur college sex videosnot obsessed with anime, but the 26-year-old entrepreneur is fascinated by people who are. In fact, that fandom is exactly what inspired him to create a startup that now boasts millions of users.

Walking around the Prudential Center in Boston four years ago, Anderson and his then-classmate at Northeastern University, now-cofounder Yin Wang, came across thousands of attendees of Anime Boston. The convention draws 30,000 people to the city every year.

“They completely took over the mall, these people all dressed in costumes. For me, it was this crazy experience of all these complete strangers around the world converging and making friends, but for my cofounder, he was like, ‘These are my people,’” Anderson said.

While Anderson personally loved robotics and studied business in college, Wang enjoyed anime and earned a Ph.D. in computer science.

Their experience sparked an idea to create communities that could mimic the enthusiasm of being at a convention but did not require tickets, travel or costumes. Instead, it relied on the smartphone.

The result: Amino, an ecosystem of mobile apps that are all focused on specific topics. On the app, users can scroll through a front page of curated posts, message in a public chatroom and see posts from people they follow.

Back in 2012, the founders under their company Narvii launched the first apps on anime, K-Pop and photography — for example. Amino grew from 15 apps in July 2014 to 41 apps a year later and now boasts more than 90 apps.

The concept of online, niche communities is not new. Reddit, referred to as “the front page of the internet,” has been around for more than 11 years and has tens of thousands of subreddits.

But the focus on mobile-first communities excited investors. Narvii, with with 25 employees based in New York and Shanghai, has raised $8.4 million in venture capital funding led by Venrock and Union Square Ventures.

“Ben and Yin believed that mobile needed to have a passion vertical,” David Pakman at Venrock told Mashable. “There is Reddit, but Reddit is somewhere between abuse and annoying for most people and not super mobile friendly yet. These guys were like, ‘Let's make it safe, friendly and mobile.’”

Amino is not directly competing for users from Reddit. Less than 10 percent of its users are also active Reddit users, according to a survey by Amino.

Pakman noted the BBC show Doctor Whoand the musical Hamiltonas two passions that have resonated with Amino users. “I have not found a better community on Hamilton than one of the many on Amino. They have one on the Schuyler Sisters,” he said.

It isn’t just Hamilton. The Anime community has more than 1 million members and the more recently-minted Pokemon Go has more than 630,000 members.

Ren Nocturn, a moderator on Amino, said the apps provide her the fandom she never found on other online forums. She is a part of five communities on anime, metal music, Harry Potterand Game of Thrones.

“Facebook just doesn’t provide the news that I’m interested in. It doesn’t provide the conversations that you’re after. It’s nice because your friends are there, but your friends aren’t always into what you’re into especially the level that you’re into stuff,” Nocturn said.

Unlike Facebook, Amino allows Nocturn to remain anonymous.

Despite enthusiasm from investors, Amino has yet to generate revenue. The startup has discussed partnering with brands, showing ads and selling digital goods. Narvii planned to start money-making strategies after Amino reached more than a million users, Anderson told Forbesback in 2013.

There appears to be no immediate rush. Amino is “definitely focused on growth."

"We see huge opportunity if we can make it a global phenomena. We’ve been fortunate enough to gather investors who believe and understand that model,” Anderson said.

Indeed, Union Square Ventures is the same firm that backed other slow to monetize but quick to grow social apps — Twitter, Tumblr, Foursquare and Zynga.

Amino is now undergoing its next phase of growth. In July, Amino released a main app, or portal, where anyone can create a community. One month later, there are more than 65,500 communities with more than 1,000 being created every day.

The users — which are in the millions but Amino declined to close exactly how many — have increased their time spent in communities from 40 minutes to more than an hour per day. For comparison, people spend 13 minutes on Reddit, 25 minutes on Pinterest, 30 minutes on Snapchat and 50 minutes on Facebook.

Discoverability has also expanded. In July, Amino users were a part of 1.2 communities, on average. That number is now up to 5.7 communities.

Prior to the portal, people would uncover the apps by searching for keywords in app stores, like Nocturn did with anime. Now, the portal suggests communities to join.

That does not mean apps are over for Amino. Big communities will still be spun into their own apps, Anderson said. The company plans to create at least 100 new apps by November, having already launched more than 20 since July. Amino is also looking to grow internationally by releasing apps in Spanish and Portuguese.

“We feel as though every human on earth could be on Amino,” Anderson said. “We’re just really excited that our big bet is starting to pay off. Our hypothesis that people want to create these communities is turning out to be true.”