Narikin Shouka Monogatari: Tsundere Ojisan wa Bijin na Toshishita Josei o Iyaiya Metoru

"Jeweler Alfonso's fourth wife, Mercedes, is a beautiful woman with an unusual background as a former knight. However, having had an unfortunate upbringing and been divorced three times, Alfonso distrusts women and shows no signs of acting like a newlywed. Mercedes, on the other hand, diligently fulfills her role as the mistress of the house, but she is troubled by her husband's inscrutable emotional fluctuations and his reluctance to open up. 'Every couple overcomes trials before they can become a family'—this is the revelation Mercedes receives as she begins her search for what it truly means to be a 'real couple'…"

(Source: Futami Shobo, translated)