SHIO TSUYAMA (Asami Mizukawa) is a 30 year old office worker who leads an unostentatious life in Tokyo. Though she has no boyfriend and no real social life, she is always smiling. Because a smile, she believes, can somehow prevent anymore of her happiness from slipping by.

One day, she makes a serendipitous discovery on her way to work. It is a sign that reads "WANTED: HOUSEMATE"--and in a big leap to change her drab life, she decides to move in. Shio's new housemate is TAPPEI (Yo Oizumi), a 38 year old male who has a positive attitude and likes to joke around that he is from outer space. Few months later, by a twist of fate, Shio acquaints herself with YUKIYA (Shousuke Tanihara), a 40 year old mysterious man who has been laid off from his white collar job. Having left his wife and son back home, he ends up homeless until Shio offers him a safe haven in their house share. From then on, Shio's new life with two different men begins...

3-in-1 House Share is an uplifting modern love comedy that depicts a love triangle between two men and a woman, set in a house shared by strangers--a relatively new lifestyle that is becoming popular in Japan due to social isolation and need for companionship. The lead role is played by talented actress, Asami Mizukawa, and co-starring as the male housemates are Japan's leading comedy actor, Yo Oizumi, and ex-model and actor, Shousuke Tanihara.