Saioshi No Gikei Wo Mederu Tame, Nagaiki Shimasu! 1 (&arche)

[Machine Translation] Alba is reborn as the son of a poor nobleman. He is unable to use magic due to a disease, and his life is doomed to be short, so he is taken in by a duke. There, he meets Orsis, who was his "most favorite" in a previous life. The most favored person in his previous life is his brother-in-law? Such a life is too good to be true! But then Alba remembers that she is the cause of her beloved brother-in-law losing his smile, and begins to search for a way to live a long life in order not to lose his smile and to continue loving him. She lectures her father-in-law, who has always had a hard time with Orsis, searches for medicinal herbs to cure her illness, and praises her brother, who has low self-esteem....... While Alba, who loves her brother, is running around frantically in such a way, Orsis is evolving more and more into a brother fool! The story is about a man who is a little bit of a fool, but he's not a fool.

貧乏貴族の息子に転生したアルバ。病のせいで魔法も使えず短命な運命を背負った彼は、公爵家に引き取られることに。そこで出会ったのは、前世で「最推し」だったオルシス。「前世の最推しが、義兄!? そんな人生美味しすぎる!」と思ったのも束の間、愛する義兄の笑顔が失われる原因が自分にあることを思い出したアルバは、オルシスの笑顔を失わないため、そして彼を愛で続けるために長生きする方法を模索し始める。オルシスにはツンだった義父をお説教したり、自分の病を治す薬草探しをしたり、自己評価の低い兄を褒めまくったり……そんな風に兄様大好きなアルバが必死になって駆け回っていると、なんとオルシスがどんどん弟馬鹿に進化していって――!?