A Saju "Brain Map" Went Viral in Korea. The Money Is in 990-Won AI Readings

On the morning of Oct. 11, 2026, the counter on Hongsimdang's "saju brain map" page read 536,676. The page is a free personality test built on saju, the Korean name for the four pillars of destiny, or bazi, read from your birth date and hour. You enter your sex and birth date, the hour if you know it, and no account is needed. The site turns the balance of "ten gods" in your chart into everyday preoccupations, such as words and action, trust, reassurance, caring for others, and rivalry, and stacks them inside a cartoon head to show what your mind reaches for first. The image is made to be saved and shared. Send the link to a friend or partner, and once they agree and add their own birth date, you see how they read you and a compatibility score for your two brains. The site's own notes say it does not reveal anyone's real feelings, is not a psychological test, and keeps each person's birth details hidden from the other.

The operator explained on Naver Blog on Oct. 10 how it took off. The brain map was finished in August and went nowhere; the operator's own posts on X drew few views. So they asked a friend who is active on X to post it. That post, by the operator's count, reached 4.57 million views and 25,000 reposts, the brain maps passed 500,000, and more than 10,000 people were on the site at once within half an hour. Those numbers are the operator's own, and we could not find the original post, but the counter we saw a day later was already past 530,000. The Korea Herald, in an Oct. 9 story on Koreans using AI to read their saju, noted that the brain map had drawn attention that week.

The free image spreads; the AI behind it gets paid. In the same post, the operator says paid orders rose with the traffic: 73 reviews and 173 repeat purchases in seven days, with no paid advertising. The paid readings are AI saju, the post says, built to read as if the operator had done them by hand. Hongsimdang's homepage says the operator has read for 682 people in person since 2020, and a pinned June post on the blog answers the obvious question in its title: AI saju, made by someone who spent four years doing readings face to face.

Another map that spread across Korea in August works the same way. Saju Doryeong's "benefactor map" puts your chart at the center. You share a link, friends join with their own birthdays, and the site labels each one: the benefactor who saves you, your right hand, the "tiger teacher" who toughens you up. A Naver blog post on Aug. 16 described people passing their maps around on KakaoTalk, and the Korea Herald said the map went viral in August as users invited friends to sign up to see how well they matched. The map is free. The readings on Saju Doryeong's homepage, from your own chart to love luck, couple compatibility, confession advice and the odds of getting back with an ex, cost 990 won each, and the site footer files them under AI saju readings.

990 won is about 70 US cents, and it has become a common price among Korea's AI saju sites. Sajuham's "future spouse face" reads the spouse palace in your chart, infers looks, mood and age range, and has AI draw a face, also for 990 won; its FAQ says the result is a reference image, not a photo of a real person. Saju Kid puts "990-won original saju" in its page title, says it is used by 1.8 million saju fans, and offers one free chat a day. Among the testimonials on its homepage, one user says that although it is AI, it listens accurately and warmly, which is why they are topping up again. A JoongAng Ilbo story on Sept. 29 was headlined on the site's 6 billion won a year from 990-won readings, and on its founder, a former mid-level government official.

The Korea Herald linked the wave to vibe coding, where people with little programming experience describe what they want and let AI write the code. Its example was a saju site built with Claude by an influencer called Roro, which caught on on Oct. 7 and then went down under the traffic; we could not find its address. None of the sites above say which AI they use to build the site or write the readings.

If you want to play, the brain map and the benefactor map are free, need no account, and are designed to be sent to friends; the sites themselves say they cannot tell you what anyone really thinks. The thing to watch is the row of 990-won buttons behind them. Each one is cheap, and tapping through one after another takes no effort at all. One testimonial on Saju Kid's homepage comes from a user who says they have spent 300,000 won on that site alone.