Building K-Saju 1: turning Korean saju into K-culture character cards

What if saju became a side project?

Lately, I found myself getting interested in saju.

At first, it was not a grand product idea. It was more like casual curiosity. I looked up a few readings, compared how different services explained the same birth information, and slowly became interested in the structure behind it.

Saju is a Korean name for a traditional East Asian birth-chart system. It uses a person’s birth year, month, day, and hour to describe patterns in personality, relationships, timing, and life direction. In Korea, many people have at least a passing familiarity with it. Some people take it seriously. Some treat it as entertainment. Many use it somewhere in between, the same way people might talk about MBTI, zodiac signs, or personality tests.

While looking into it, I had a small thought:

Could this become a web service that feels light, modern, and fun instead of heavy or mystical?

That question became the starting point for K-Saju.

I did not want to build a service that tells people, “This is your fixed fate.” That kind of tone can feel too serious, especially for someone outside Korea who has never heard of saju before. I wanted the experience to feel closer to a playful self-discovery tool: something you can read, smile at, share with a friend, and still feel that it came from a real Korean cultural idea.

So the project became less about translating saju word-for-word, and more about turning it into K-culture character cards and chemistry tests.

Using K-culture as the doorway

The first audience I imagined was not someone already studying saju. It was someone who likes K-pop, K-drama, Korean culture, personality quizzes, or relationship tests.

For that audience, terms like “Four Pillars” or “Myeongri” can feel abstract right away. Even the word “saju” needs context. If the first screen feels like a traditional fortune-telling service, some people will leave before they ever get to the fun part.

So I tried to change the doorway.

Instead of presenting the service as a strict traditional reading, K-Saju uses phrases that are easier to enter:

• Saju -> K-Saju Birth Chart
• Five elements -> Element Balance
• Compatibility -> Chemistry

This is not about erasing the original meaning. It is about giving a new visitor enough comfort to start. Once they are inside, the experience can still point back to the structure of saju, but the first impression should feel friendly.

I also wanted the result to avoid deterministic language. The result should not say, “Your destiny is this.” It should feel more like:

• “You give off this kind of K-drama character energy.”
• “In a K-pop group, you might naturally play this role.”
• “Your element balance suggests this kind of vibe.”
• “Your chemistry with a friend has these easy points and these tension points.”

That framing matters. It keeps the service in the space of entertainment, self-reflection, and conversation. For an international audience, that feels more natural than asking them to believe in a cultural system before they even know what it is.

One more important choice: I did not want to use real idols, actors, or drama characters directly. That would make the service feel like it is borrowing someone else’s identity. Instead, K-Saju uses broader K-culture archetypes: the leader type, the quiet strategist, the scene-stealing friend, the warm main character, the mysterious second lead energy, and so on.

Those archetypes are familiar enough to feel fun, but general enough to belong to the product itself.

Making it feel like Piyak Labs

The visual direction became just as important as the product idea.

Piyak Labs has a small yellow chick mascot. The name “piyak” comes from the tiny sound a chick makes in Korean. To me, that mascot fits the feeling of building side projects: starting small, learning in public, making something imperfect, and slowly letting it hatch.

I wanted K-Saju to carry that feeling too.

Saju can easily look heavy if the design leans too far into mysticism: dark colors, ancient symbols, dramatic fortune-telling language. That may work for some products, but it was not the tone I wanted here.

With the yellow chick as the center, the mood becomes much softer. A result card can feel less like a prophecy and more like a character poster you just hatched. It can still have meaning, but it does not need to intimidate the user.

That led to a few design principles:

• cute, but not childish;
• closer to K-culture character cards than traditional fortune charts;
• different result types should have different images and moods;
• the shared card should make the Piyak Labs brand easy to remember.

For the result images, I decided not to generate a brand-new AI image every time a user submits the form. That would make the experience slower and harder to control. Instead, I am mapping each result type to a prepared visual style. It is faster, more consistent, and easier to make the service feel like one coherent world.

What went into version 1.0

K-Saju 1.0 is built around two main flows.

The first is My K-Saju.

The user enters their birth information and gets a personal K-Saju type, an element balance, a role they might play in a K-pop-group-style team, and a K-drama-like character interpretation. The output is designed as a card, because I wanted it to be easy to read and easy to share.

The second flow is Friend Chemistry.

A personality result by itself can be fun, but it often ends there. The moment a user thinks, “I should try this with my friend,” the product becomes much more social.

So I added a one-to-one chemistry flow. It can be used with a friend, a partner, or even just someone you are curious about. The goal is to describe where two people connect naturally, where they might create tension, and what kind of story their combination suggests.

Again, I tried to keep the wording light. The service should not sound like it is making final judgments about relationships. It should feel like a small cultural game: a fun way to start a conversation.

You can try it here:

Open K-Saju

What I want to build next

K-Saju has just reached its first 1.0 shape. Right now, the core experience is open: a personal K-Saju card and a friend chemistry test.

The next step is to make the reading deeper without making it feel heavy. I am thinking about richer relationship interpretations, more detailed personal readings, and result pages that feel more like collectible character cards.

I am also thinking about premium features, but the tone still matters. I do not want K-Saju to become a scary fortune-telling product. I want it to stay closer to K-culture-based self-discovery and relationship play.

This post is the first part of the K-Saju build story. I wanted to write down why I started the project and how the idea became more concrete.

In the next post, I plan to talk more about the product and development side: how I structured the birth-information flow, how I mapped results into K-pop/K-drama-style roles, how the result cards are composed, and what I learned while turning a cultural idea into a small web product.

There is still a lot to improve. But like the Piyak Labs chick, I am building it one hatch at a time.

If you try K-Saju, feedback is always welcome.