Coffee plays an opposite role to alcohol. Like people would say "drinking this early?" if they saw you at 11am with a bottle in hand, it would be "coffee this late?" at 11pm if you offered. It wakes you up, instead of making you sleepy, but you'll often find yourself sipping this friendly, social drink at late hours in the lively city of Seoul. Coffee is great at any time, with anything, with anyone, or will make fine company with a book or a relaxing moment alone.
Ah, coffee, how did the world go 'round without you?