He is the doctor that helps Taki and, later in the manga, Miyuki from Dr Ashino. According to Taki, he is a qualified medical doctor, pediatric, plastic surgeon and esthetician, and according to himself he is also a gynecologist as a hobby. He is never named in any other way than "Doctor" aside from his girlfriend calling him Masataka once.
He appears in the first episode of the anime where he play largely the same role.