From MangaHelpers:

Life does not always go as planned. Noriko fell in love, got engaged, and imagined a bright future. Instead, her fiance fell in love with her older sister, Eiko. Noriko refused to let go, and they ended up getting married despite this significant problem. Some years of marriage and two children later, Noriko became a single mother. She returned to her family home, with her daughters Eri and Madoka. Her life continued, alongside Eiko (who ended up never marrying or leaving home), and their now elderly mother. Years later, Eri and Madoka are entering the time of life where they have their own problems with love. This manga follows the lives of women in this house. [tethysdust]