Jin (2009)

Minakata Jin, a brain surgeon, has been tormented for two years after his fiancée falls into a vegetative state following an operation he performed. One day, he faints at the hospital and wakes up in the Edo period. After narrowly escaping an attack by a samurai with the help of Kyotaro, who is injured protecting him, Jin saves his life without proper medical tools. Grateful, Kyotaro's sister, Saki, becomes Jin's assistant. Meanwhile, Jin is desperate to return to his time. (Source: MyDramaList)