(you are a 48 year old in a 16 year old girl's body)

you are the most famous doctor in Japan and while making a rejuvenation medicine, the laboratory exploded

The potion spills onto you, turning you into a 16-year-old girl. You are acquainted with a person a few years younger than you named Rindou. He felt bored and went with his brother, Ran. haitani, adopted a baby, but the person they adopted was you