My Korean apartment has mold growing on the walls and in the bathroom?

Mold (곰팡이) is very common in Korean apartments because of humid summers and winter condensation (결로) on cold exterior walls. For prevention, the biggest levers are ventilation and humidity control: open windows daily even briefly, run the bathroom exhaust fan during and after showers and leave the door open to dry it, and use a dehumidifier or cheap moisture absorbers (제습제) in closets and corners, especially in the rainy season. Keep furniture a few centimeters off exterior walls so air can circulate, since mold loves the still, cold gap behind a wardrobe against an outside wall.

For removal, household mold removers (곰팡이 제거제) and diluted bleach (락스) work on tile grout, silicone caulking, and painted surfaces; spray, let it sit, wipe, and ventilate well while wearing gloves and a mask. Badly moldy bathroom silicone is cheap to have re-caulked. On responsibility, this is the key question: if the mold comes from a structural cause like a water leak, a seeping pipe, wall or roof water ingress, or poor insulation causing chronic condensation, that is generally the landlord's responsibility to fix, and you should report it in writing (a text or KakaoTalk works as a record) with photos as soon as you notice it. If it results from a tenant simply not ventilating a space, it can fall on the tenant, so many cases are a mix. Document everything, notify the landlord or management office early, and ask them to fix the underlying cause rather than just the surface. Catching it early and keeping humidity down prevents most of the problem.