The drama tells the story of three sisters aged 19, 29 and 39, who gather under the same roof in the last year before reaching the "age mark", that is, the "9th line", with their father's sudden disappearance as an opportunity. The drama is based on the "3L" theme of "LOVE", "LIFE" and "LIMIT", and describes their life attitude of struggling and moving forward while searching for happiness with confusion and anxiety.