Korean Coach stores your Google-verified email (your account id), your Korean practice history and spaced-repetition progress, and short notes you ask it to remember. This data is used only to run your lessons and is kept in Google Firestore.
Payments are handled by Paddle, the merchant of record; we never see your card details. Ask anytime to erase your memory in-conversation, or contact contact@poietic.studio to delete your account.