Lee Wan and Hwa-ran, a couple in their twenties with nothing to their name, dream of brighter futures—Wan as a rapper and Hwa-ran as a webtoon artist. After leaving their cheap lodging, they decide to live together. However, their new home, secured with a loan, turns out to be a scam by the real estate agent, forcing them to move into a mold-infested basement. Can they protect their dreams and love while trapped in this underground cave and find a way out?