Washing windows on a space colony hovering 35,000 meters above the earth is a dangerous job. Mitsu, a young window washer, knows this all too well. His father fell off the Ring System in an accident. Now, Mitsu's coworker Kageyama collapses on the job. Trying to save Kageyama, Mitsu inadvertently endangers his life. In recovery, Kageyama learns that exposure to UV rays has taken a toll on his immune system. He's forced to choose between his job and his health.