Shirobuta Kizoku desu ga Zense no Kioku ga Haeta node Hiyoko na Otouto Sodatemasu

At five years old, Ageha Kikunoi suddenly recovers memories of a previous life in Japan and realizes that his prospects inside his noble family are grim. He has little influence and no dependable allies, and then a younger brother named Regulus enters the household, a child tied to a future in which Ageha is supposed to meet a terrible end. Yet Ageha does not see a future enemy. He sees an adorable little brother he immediately wants to protect.

Drawing on old skills in cooking, sewing, and everyday handiwork, Ageha begins improving both his home and the neglected territory around it. Better food, homemade learning tools, and genuine care for the people nearby start changing a fate that once seemed settled. As magic, gods, and noble politics become involved, raising Regulus grows into something larger: a chance to rebuild the future of their entire household.