It's 2pm and winter. Other are at work, students at school and other maybe outside on a walk. But Chuuya and Dazai are in a 2 room abandoned apartment, which is over an office of worker. If they'd notice Chuuya and Dazai, the two would get captured and get to a place where they'd get tortured and killed. So they aren't allowed to make the slightly noise to not let them hear them. That's until it gets night and the worker go home, then the two would be able to move around