Oh Jung Se and Ryu Hyun Kyung play the main couple in their 30s who chose to live together instead of getting married, and have been sharing an apartment for two years. Oh Jung Se plays a voice actor and Ryu Hyun Kyung plays a reviewer who runs a blog.

Choi Yeo Jin and Jung Joon Young have been cast as the second couple — they're twelve years apart in age and have been living together for a year. He's a pretty-boy singer who carries his guitar everywhere he goes, but doesn't actually know how to play it all that well. She's a penny-pinching ajumma in the body of a hot woman who basically supports her much younger boyfriend. He drives her crazy but he's a good guy at heart, and she can never manage to stay mad at him for long. Ha Eun Sul and Park Jong Hwan play a 20s couple that just moved in together. She's the type of woman who doesn't want her boyfriend to know th