SEOUL, South Korea — The sunlight peeks into Kim Ssang-seok’s home for just half an hour a day. When he opens his only window and looks up, he sees the wheels of passing cars. Mr. Kim dries his clothes ​and shoes ​in the sunless inside because of thieves outside. He wages a constant battle against cockroaches and the sewer smell emanating from the low-ceilinged, musty space that is his toilet and laundry room.

This 320-square-foot abode, built partially underground, has been Mr. Kim’s home for 20 years. His late mother smiles from a portrait on the wall.

“You end up in places like this when you have nowhere else to go,” said Mr. Kim, 63, a taxi driver.

But Mr. Kim, a widower, said he was still “grateful that I have a roof over my head and a warm floor to rest on.” He fears the city will clear out his neighborhood in a few years to make room for more of the apartment towers that increasingly dominate Seoul’s skylines.

If that happens, Mr. Kim said, he has “no plan” on where to go — just like the desperate family in “Parasite,” which became the first foreign-language movie to win the Academy Award for Best Film this month.