With her older brother's sudden marriage announcement, a woman becomes a "sister-in-law". As the newlyweds move in upstairs, an unusual cohabitation begins. Two families, old and new, blend in unique ways.

Despite familial ties, they remain unfamiliar. The sister-in-law's lively personality brings a breath of fresh air. An adorable nephew's arrival adds to the change, revealing hidden family aspects. Amid these new relationships, the family's identity takes on a new dimension.

This is the physical copy of the Lower Floor Sister-In-Law manhwa.