Cream Lemon: Magic Doll (2007)

Shoko, Ryuta's ex-girlfriend, is left brain dead after a traffic accident. Shoko's brother and Ryuta were classmates and best friends in medical school. One day, Ryuta receives a request to track down a famous person who has gone missing. That person is Shoko's brother, a genius doctor and artificial intelligence researcher, only 25 years old. He was a rising star who had published one groundbreaking paper after another and was hailed as someone who would fundamentally change the world of artificial intelligence, but he disappeared a year ago, betraying the expectations of those around him.