Naosumi Kido is a professor at Tokyo College of Music and one of the suspects in Quartet with Intent to Kill. He has been teaching violin to Akechi since he was four years old, and as the number one disciple he buys Akechi's violin talent. A violinist was involved in a traffic accident at the Rose Festival, a cultural festival of Tokyo College of Music, and Akechi was urgently requested to act as a substitute. His full name was not given in the original, and he was called Professor Kido.