Isekai Yakkyoku

After losing his little sister to an incurable disease, world-famous medical researcher Kanji Yakutani gave it his all to cure patients by dedicating his life to inventing new medicines. After working himself to death at the age of 31, the former pharmacist wakes up as a 10-year-old child whose body has been struck by lightning. He discovers that he has been reincarnated into a medieval world as Falma, a child of the respected De Médicis family.