Sajunote — AI-personalized Korean saju (Four Pillars of Destiny) readings

What we build

Saju (사주, "Four Pillars of Destiny") is a traditional Korean way of reading a person's character and life timing from the year, month, day and hour of birth. Each pillar is a pair of a Heavenly Stem and an Earthly Branch, and the balance of the five elements across the eight characters is the basis of the reading. Traditionally it is read in person, and most saju apps return fixed text per chart type.

Sajunote makes the reading personal and explains it in plain language:

1. Chart calculation. From the birth date (solar or lunar calendar), birth time (or "time unknown"), our engine computes the four pillars, five-element balance, ten gods, major luck cycles (대운) and yearly luck. This part is code, not AI, so the same input always gives the same chart.
2. Personalized reading. The computed chart, plus the worry or question the user writes in, is given to a large language model that writes the reading section by section — personality, relationships, money, career, health and timing — grounded in that specific chart.
3. Quality checks before display. Automated checks reject text that does not match the computed chart, is too shallow, or is broken, and regenerate it before the user sees it.
4. Delivery. Results open on the web page right away; the full report is delivered as a PDF to the user's email within 24 hours of payment.

Products (prices in Korean won)

Payments are processed by Toss Payments. Login, when needed for credits, uses Kakao. Product line-up and prices are those shown at checkout and may change.

How we use AI — building on Claude

AI is both how we build Sajunote and what the product delivers. Below, what we do today is marked separately from what we are building next.

The technical problems we work on

• Long personalized documents. A Book of Destiny report is 100+ pages in 12 sections. Every section has to stay consistent with one chart and one person, without repeating itself across sections.
• Grounding. The model must use the facts our engine calculated (pillars, elements, luck cycles) and must not invent its own chart. We check each section against the computed chart before accepting it.
• Prompt caching. Every section of a report shares the same long context — the chart, the user's worry and the writing rules. Caching that shared prefix is how we plan to keep cost and latency of a long report under control on the Claude API.
• Automated quality review. Generated text passes gates for minimum depth, broken or garbled text, name handling and consistency, and failing sections are repaired and re-checked before delivery.
• Latency on mobile. Most users arrive from mobile and in-app browsers, so the free reading has to start showing quickly while the longer sections are generated in the background.

Company

Company name

Sajunote (사주노트)

Founded

December 2025

Founder & CEO

Hyekyeong Han (한혜경)

Location

Hwaseong, Gyeonggi-do, South Korea

Business registration no.

405-21-02469

Mail-order sales registration

2026-화성동탄-0037

Address

902-R122, Pil Plaza, 37 Dongtanjungsimsangga 2-gil (Bansong-dong), Hwaseong-si, Gyeonggi-do, Republic of Korea
경기도 화성시 동탄중심상가2길 37, 902호-R122(반송동, 필프라자)

Email

help@sajunote.kr

Phone

+82 10-7405-4368 (010-7405-4368)

Website

https://sajunote.kr

한국어 요약