In a hanok alley in Ikseon-dong, Seoul, stands Dal Bubble, a tiny milk tea café that is closed every Monday. The regulars think owner Seo Ji-hoon just takes his day off seriously. The truth: on Mondays, from noon to midnight, his front door opens onto another world — the Moonflower Meadow of Avelion, where the café has been a legend for fifty years as the Pearl Dew House. Knights, archmages, dwarf smiths and one ancient dragon queue politely for brown sugar, cheese foam and taro. His only help on Door Days is Runa, a demonkin refugee who came in starving one Monday and never went home. The rules are simple: all guests are equal, no weapons, no spells, and what is said in the café stays in the café.