Sekokechi Gimai ga Subete wo Ushinatta Hanashi

The protagonist, Reimi, has one thing that makes her feel uneasy. That is, her sister-in-law, Kae, is incredibly stingy! She takes home all the decorations from the wedding, the gift envelope from her parents-in-law for the birth of her child clearly has Kae's name written on it later, and the baby gifts she sends are dirty, used baby goods... She's just so stingy!

She tells herself she doesn't really mind, and it's not that bad... and when the protagonist tries to hold back, she finally crosses the line...

(Source: Kodansha, translated)