Ready Builder One is a business club for teenagers. Underground is its small class, for six people at most.
Why underground
Upstairs, Playground is an open field where anyone can come and build as much as they like.
Underground is below it: a workshop where six people sit around one table, each wrestling with their own service.
Learning on a big stage is different from having your own work looked at in a small room.
Underground is where your child’s own service comes up, every single week.
How it differs from Playground
| Playground | Underground | |
|---|---|---|
| Size | No limit | Up to six |
| Weekly live class, VOD and community | ✅ | ✅ (all of Playground included) |
| Weekly mission feedback | From the club | From Stein Choi himself |
| Small-group session | — | Every Thursday at 5 pm, two hours (four a month): everyone presents their own service and is coached, every week |
| Care outside class | — | Focused one-to-one care, even outside class time |
| Open coaching | A chance to apply | Every week, guaranteed |
How each week runs
- Small-group session: every Thursday at 5 pm, two hours, online (based on four a month). All six present this week’s progress, and the next week’s work is set on the spot.
- Focused care outside class time: with only six, each child is looked after individually, even between sessions
- Missed a session? Nothing is lost: we send the recording and follow up with your child individually
- Sometimes offline: now and then we meet at the Gangnam studio and build together (not on a fixed schedule)
- Feedback from Stein Choi himself: he reads every weekly mission and replies in person
- All of Playground included: the weekly 90-minute live class, full recordings (VOD) and the community
- A portfolio page for every student, plus a monthly growth report: parents can check progress at any time
What your child holds after three months
| Month | What they make |
|---|---|
| Month 1 | Mission statement and service plan |
| Month 2 | Service MVP: a real thing built with free AI tools |
| Month 3 | Launch and first response: put it out into the world and meet the first visitors, followers and customers |
After launch you keep climbing the level ladder: first users, running and improving, then a second service.
We promise the deliverables, through the curriculum. We do not promise results such as visitor numbers or revenue. But your child will, without fail, experience a real response from the world.
Who teaches
Stein Choi (Wonseok Choi)
A working entrepreneur who founded and runs three companies in Korea and the US: an AI education platform, an AI character SaaS and an AI website builder.
Until now this course has only been taught one-to-one, at 1,320,000 won a month. Underground shares that intensity among six.
Who this is for
- Students who move faster when a small team pushes them than on their own
- Students who already have an idea and want to get to something real, fast
- Students who find it hard to ask questions in a big class
For: middle and high school students (upper elementary after a consultation) · No coding or design experience needed
How to join
- Six places at most. When they are full, we put you on the waiting list in order.
- Join after a consultation: a short talk with your child, then we decide together whether Underground is the right fit
- 790,000 won a month (VAT included, Playground included, based on four small-group sessions a month) · no discounts
- First-month refund guarantee: ask within 7 days of attending your first small-group session and the whole first month is refunded (not available once you have attended two or more sessions)
- Starts: first session on Thursday, November 5, 2026 at 5 pm
- Founding season only: Underground is a class we open only in Ready Builder One’s early days
Ready Builder One: Underground
Apply for a consultation
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