Do I actually need cash in Korea, or is card enough?

Card covers about 95% of what you'll do, but the missing 5% is exactly the stuff travellers come for.

Card works everywhere that matters: convenience stores, cafés, restaurants, taxis, subway (via T-money), department stores. Korea is more cashless than most of Europe. But you'll want ₩50,000–100,000 in cash for traditional markets like Gwangjang or Tongin, street food stalls, small temple entrance fees, and the occasional old-school place run by an elderly owner.

One practical warning: many Korean card terminals reject foreign cards even when they accept "international" ones — this is a known issue with certain domestic-only networks. Bring two cards from different networks (one Visa, one Mastercard) and don't rely on Amex. ATMs marked "Global" at convenience stores accept foreign cards and are on nearly every block.