My Full Conversation with Charles Yoo-Naut

At the Stablecoin Conference in Mexico City, amid discussions on the future of digital currency, Rain Co-Founder and CTO Charles revealed significant news during an impromptu interview. He announced that Rain has closed a $58 million Series B funding round led by Sapphire Ventures, with participation from new investors Dragonfly, Samsung Next, and Endeavor Catalyst, alongside existing partners. This brings Rain’s total funding to $88 million.

This new capital validates Rain's core mission: to solve the single biggest problem holding back the mainstream adoption of crypto by building the "backwards compatibility" layer for the new financial system. Rain is focused on making stablecoins, which offer near-instant and low-cost global settlement, easily spendable in the real world.

The Core Problem: "Lipstick on a Pig"

The journey for Rain’s founders began with a deep-seated frustration while building on traditional financial rails. The experience led to a powerful realization about the state of the industry. Charles describes much of the last decade of financial innovation as simply putting "lipstick on a pig."

"All of fintech for the past few decades has just been lipstick on a pig and this is actually a way to go from first principles and build like a global financial rail," Charles explains.

This perspective drove the company to address the central paradox of stablecoins. While the market cap has grown to over $250 billion and transaction volumes surpassed $5.7 trillion in 2024, their real-world utility has remained limited. As Charles notes, the technology’s promise was disconnected from practical, everyday use.

"I can send you a stable coin and that's great. It would settle in in seconds and it will cost fractions of a penny, but the things that you could do with it were really limited. You couldn't go and to a coffee shop or you couldn't buy a laptop."

This gap creates a critical "last mile" challenge, particularly for powerful use cases like remittances. A family member in an emerging market could receive USDC, reducing transfer fees from the 6.65% average on traditional rails to as low as 1-3%, but they would be left asking, "What do I do with this now?" Rain was founded to answer that question.

The Solution Strategy: From Niche Product to Global Platform

Rain’s strategy began with a clear entry point to bridge the gap between digital assets and real-world commerce.

The Wedge: Cards

The initial insight was to leverage the existing global card networks as a powerful "wedge" into the market. By enabling stablecoins to be spent via the Visa network, Rain could instantly provide access to tens of millions of merchants globally without requiring any change in merchant behavior.

"It became very clear that cards was the best wedge because if you can make stable coins spendable with cards have access to hundreds of millions of merchants globally then now we're accepting stable coins without even knowing it," Charles states.

Phase 1: Serving the Crypto-Natives

Rain first focused on building a spend management platform for DAOs and crypto foundations. These crypto-native organizations were already living on-chain and held large stablecoin treasuries but faced the same operational expense challenges as traditional businesses. This focused approach allowed Rain to perfect its core infrastructure, including stablecoin-native card settlement, achieving Visa Principal Membership, and securing necessary licensing.

The Pivotal Shift

The company soon reached a critical juncture. The true, massive opportunity was in becoming a horizontal infrastructure platform. The market for B2B and enterprise stablecoin infrastructure is already valued at over $2.1 billion and is projected to reach $17.4 billion by 2033. Rain’s own customers validated this trend.

"We just had more demand pulling us in this platform side," Charles reflects. "People either our customers or people that saw the cards that we were issuing were saying how do I embed this into my app or how do I do this for my customers... our customers kind of pulled us in that direction."

This realization marked the strategic shift from a vertical product to a horizontal platform designed to empower other businesses to launch their own stablecoin programs in markets from Bolivia to Nigeria.

The Market Impact: Powering a Global Revolution

By becoming an infrastructure provider, Rain has gained a unique vantage point into the global adoption of stablecoins, effectively serving as an index for emerging real-world use cases.

Crisis-Driven Adoption (Bolivia)

"There's a lot of interesting use cases in emerging markets that we're seeing like Bolivia for the last couple months has been one of our largest markets and they're facing a big currency crisis like people want access to dollars and to save in dollars," Charles notes.

This has made Bolivia one of Rain's largest markets, demonstrating how stablecoins can serve as a lifeline for savings and spending, moving far beyond speculation.

Government Legitimacy (Wyoming)

Rain's infrastructure is also bridging the gap between public sector innovation and real-world utility. The company recently partnered with the Wyoming Stablecoin Commission to power spending for the Frontier Token (FRNT), the first state-issued stablecoin in the U.S.

"Wyoming is the first state to launch their own stable coin, the front token," Charles says. "And then with RAIN, we're able to give all of those payees that are accepting the Frontier token a way to actually spend it."

This partnership makes the 102% overcollateralized, government-backed stablecoin spendable via a Rain-issued card for state expenses like contractor payments, providing immediate, tangible utility.

The Future of Finance (USD+)

Pushing the boundaries further, Rain has integrated with Dinari's yield-bearing stablecoin, USD+, which is backed by tokenized treasuries. This allows non-US users to blend savings and spending in a single account.

"It holds a yield bearing stable coin that's growing every day and then spending against that growing balance," Charles announced. "Instead of having like this idea of a savings and a checking account, it's like blending the two."

This integration points to a future where users can spend against a balance that is actively earning yield, a significant leap forward in financial product design.

Conclusion: Building the New Rails

To frame the future, Charles uses a powerful analogy that captures the current state of stablecoin adoption.

Rain is building that critical backwards compatibility layer today. The core technical challenge the company solved was immense: syncing the sub-second speed of a fintech card transaction with the settlement finality of multiple, disparate blockchains. This required building custom infrastructure at the messy intersection of fintech and crypto.

The $58 million Series B will fuel the expansion of Rain's full-stack enterprise offering, including wallets, payouts, and virtual accounts, delivered through a single API. The ultimate vision is to build the stablecoin-native rails that will power the next generation of global fintech, moving from bridging two worlds to defining the financial infrastructure of the future.