The answer first
Check before travelling
Official sources
The answer first
Article 28 of Korea's Tourism Promotion Act prohibits admission of people under 19. Use the date of birth and valid identification when checking age restrictions. An adult companion, hotel stay or spoken statement cannot replace an individual eligibility review.
Check before travelling
Hotel, restaurant and casino conditions apply separately. Ordinary hotel or dining access does not authorize casino entry. With younger companions, check accommodation and public-space rules independently instead of inferring access from a photograph.
Age is only a starting condition, not an admission guarantee; nationality, documents and other restrictions also matter. Meeting the local age threshold does not establish legality under applicable laws for Chinese citizens. The linked official material explains rules and offers no entry arrangement.