From a Shibuya Apartment to 2 Million Users
Marsh Harbor Deck began in the winter of 2022, in a small apartment in Shibuya, Tokyo. Marcus Thompson and Dr. Ananya Singh had been working independently on conversational AI research — Marcus at a leading NLP lab, Ananya completing her postdoctoral fellowship at the University of Tokyo. They met at a small AI ethics conference and realized they were both obsessed with the same question: why did interacting with AI feel so hollow, so transactional, so fundamentally unsatisfying?
The problem, they concluded, was not intelligence. The models were becoming extraordinary. The problem was memory, context, and emotional coherence — the things that make a conversation feel like it actually matters. They began building experiments together on weekends. Gabriel Santos, a mutual friend and interaction designer, joined them after seeing early prototypes. David Nakamura came on board three months later to build the infrastructure capable of scaling their vision.
In April 2023, they incorporated Marsh Harbor Deck Co., Ltd. in Tokyo. The first version of the product launched quietly to a private beta of 200 users. The feedback was unlike anything they expected. People were writing messages at 2 in the morning to say thank you. They described feeling genuinely heard for the first time in years. Some were isolated by circumstance — geography, disability, social anxiety. Others simply craved deeper intellectual engagement than their daily lives provided. Marsh Harbor Deck met them where they were.
Public launch came in September 2023. Within 90 days, Marsh Harbor Deck had 100,000 registered users. By mid-2024, that number crossed 500,000. The team grew from four to forty, then forty to two hundred. New offices opened in San Francisco and London. Partnerships with global content creators brought fresh perspectives and voices into the companion library. In early 2025, Marsh Harbor Deck raised a Series B round, allowing the team to invest deeply in proprietary model development, data infrastructure, and the safety research program that continues to define the company's reputation.
Today, with over 2 million active users across 48 countries and 500+ unique AI characters, Marsh Harbor Deck is widely recognized as the world leader in meaningful AI companionship. But the founding team insists they are only getting started. The conversations being had on Marsh Harbor Deck every day — millions of them, spanning every language, every culture, every life stage — represent something genuinely new in the world. That is the thing that keeps everyone working late into the Tokyo night.
