I almost got into YC with this startup
Instead, I ended up investing in them, and the story is crazy 🔥
Hey everybody, welcome back to The AI Opportunity.
Today I’m sharing something different: the story behind my latest investment.
Three years ago I went to an AI hackathon as a judge.
It was one of my first weeks working in VC, and I was basically saying yes to anything that helped me meet people. I helped organize the event with a friend who ran a local coder community.
Back then I was completely broke. I never planned to stay in VC; I just needed money and wanted to be around founders so I could eventually build something myself. ChatGPT had just launched, everyone was experimenting, and the whole thing had that chaotic early-AI energy.
One of the developers built a really cool project, I don’t even remember the exact details, something like a personal assistant, but I voted for him and he ended up winning the hackathon (or maybe second place, my memory is messy).
Fast-forward one year.
I’m in San Francisco trying to figure out my life with no plan, messaging anyone who would meet me, sleeping on the sofa of a YC founder friend. Total chaos.
Then I realized the same developer from the hackathon was now working at a YC startup in SF, his name is Toni,
Total coincidence.
I messaged him, we met in his office, and we instantly clicked. He was self-taught, building since he was a kid, and had moved to the US because people like him didn’t really have a place in Spain yet.
We stayed in touch.
Months later we met again in New York, where his company had another office. His best friend, Pablo— the COO — was there too.
They were thinking about starting their own company, and I spent months talking to Toni whether I should join them.
He was in a very similar situation to me, coming from a small town in Spain where tech and globally ambitious people were inexistent and with a huge drive to learn about the world and achieve our dreams.
I almost quit GoHub to do it, but I wasn’t ready yet, so in the end I didn’t.
A few months later they got into YC. Not only that, they became one of the top companies in the entire batch.
Today they’re absolutely crushing it. And I was super luck to be able to become their investor.
Karumi AI is one of those rare stories where everything comes full circle in a way you could never script. From a random hackathon in Valencia… to SF… to NYC… to YC… to now backing them as they build something huge.
What Karumi AI Is Building (and Why It’s Exciting)
Karumi is building a new way for companies to show their product:
AI-powered, interactive product demos that feel like a live walkthrough, but don’t require a human on the other side.
The core idea is simple:
Prospects want to see the product instantly.
Sales teams can’t be available 24/7.
Traditional demo funnels create too much friction.
Karumi solves this gap.
Their platform lets companies create dynamic, step-by-step demos where an AI agent guides the user, explains features, asks questions, adapts the flow, and delivers a tailored experience.
Not a static video.
Not a generic screen recording.
Not a chatbot.
It’s an adaptive, interactive demo that responds to the user and walks them through the product in a way that feels conversational.
Think of it as the evolution of “Watch a demo” into:
“Try the product with an AI guide who adapts to you.”
What This Unlocks
visitors get an instant, personalized walkthrough
companies capture interest at the exact moment of intent
sales teams save hours on repetitive explainer calls
global reach (any language, any timezone)
demos become scalable assets
And because the system is interactive (not linear), each user sees a demo tailored to their needs: onboarding, feature explanation, pricing flow, integrations, use cases. All dynamically routed.
Why I’m So Excited About Them
I’ve known these founders for years, long before Karumi existed. Every time we crossed paths (in Spain, SF, or New York) they were building something meaningful. No noise. No ego. Just output.
Seeing them now, fully focused on a problem this big, feels like the natural progression of everything they’ve done so far.
And the timing is perfect.
The market wants faster buying cycles.
Teams want fewer repetitive calls.
Buyers want to see the product instantly.
Karumi sits right at that intersection.
This isn’t a lucky idea or a random pivot. It’s the right founders meeting the right problem at exactly the right moment.
That’s why I invested.
And why I think they’re just getting started.
It’s a bet on two exceptional builders.
Can’t wait to see what they do next 🔥
Best,
Guillermo
PS: Let me know if you want an intro to them!
FAQs
About the founders & the backstory
Who are the founders of Karumi AI?
Karumi AI was founded by Toni and Pablo, two Spanish builders who previously worked at a YC startup. They are self-taught engineers with years of hands-on product experience and a track record of building since they were teenagers.
How did the investor first meet the Karumi AI founders?
The relationship started at an AI hackathon three years earlier, where Toni presented a project and won/placed highly. Coincidentally, both reconnected later in San Francisco, then again in New York, which ultimately led to the investment.
What’s the story behind the investment in Karumi AI?
It’s a multi-city, multi-year relationship that began at a hackathon in Valencia and continued across SF and NYC. The trust built over years made investing a natural consequence once the founders launched Karumi AI.
About Karumi AI’s product
What does Karumi AI build?
Karumi AI builds AI-powered interactive product demos that feel like a real live walkthrough — but without needing a human from the sales team.
How do interactive AI demos work?
Users interact with an AI guide that explains features, asks questions, adapts to the user’s needs, and dynamically adjusts the demo path in real time. It’s not a video or a screen recording — it’s a conversational, adaptive experience.
How is Karumi AI different from traditional product demos?
Traditional demos are linear, static, and depend on human availability. Karumi AI demos are:
adaptive
conversational
personalized
available 24/7
multi-language, multi-timezone
They compress the “watch a demo → book a call” funnel into a single interactive touchpoint.
Can Karumi AI demos replace early-stage sales calls?
They can replace the repetitive, top-of-funnel explainer calls by giving prospects immediate clarity on product value — freeing sales teams to focus on higher-intent conversations.
Value proposition & market
Why do companies need AI-guided product demos now?
Buying cycles are getting shorter, prospects want instant product exposure, and teams want to automate repetitive demo calls. AI demos match the pace of modern SaaS buying.
What business problems does Karumi AI solve?
Karumi AI:
reduces friction in the demo funnel
increases conversion from website visitors
saves sales teams dozens of hours per week
allows buyers to self-qualify
enables global go-to-market (any language, any timezone)
Which companies benefit most from Karumi AI?
Best fit: SaaS companies with complex products, PLG motions, global customers, or high demo volume (DevTools, B2B SaaS, cybersecurity, data tooling, AI platforms).
Is Karumi AI good for PLG companies?
Yes — PLG motions rely on reducing friction. Karumi AI provides immediate product exposure while still collecting insights and qualifying leads.
YC & credibility
Is Karumi AI a YC startup?
Yes. The founders were accepted into Y Combinator and became one of the standout companies in their batch.
Why did YC invest in Karumi AI?
Because the founders have a strong builder background, the problem is big and urgent, and early traction showed the product solves a clear go-to-market pain point for SaaS companies.
Investment & founder alignment
Why did the investor decide to invest in Karumi AI?
Because the founders consistently demonstrated output, resilience, and clarity over years — and the problem they’re solving is timely, underserved, and directly tied to revenue for SaaS companies.
What makes the Karumi AI founders exceptional?
They are self-taught, product-obsessed, and globally ambitious. They execute fast, avoid noise, and focus on solving real problems rather than chasing hype.
Practical questions
How can I contact or get an intro to Karumi AI?
The investor offers intros upon request — readers can reach out directly to get connected with the founders.
Can Karumi AI demos be customized for different verticals?
Yes — companies can create flows for onboarding, feature explanations, pricing, integrations, security, and custom use cases.
Really interesting stuff, Guillermo. Your own personal story reminds a bit of my own actually - although different location, different pathway.
Thank you for sharing !