When his father was transferred to Germany for further studies, Funahashi was entrusted to the care of his grandmother in the Koshigoe neighborhood of Kamakura, Kanagawa, where he spend most of his youth.

His literary coterie included Tomoyoshi Murayama, Tomoji Abe, Ujaku Akita, Masuji Ibuse, Motojirō Kajii and Shigeru Tonomura, and his early works and activities with the Shingeki movement drew the attention of Hidemi Kon and Hideo Kobayashi.

By 1940, Funahashi had joined the government-sponsored Literary Home Front Drive (Bungei Jugō Undō) along with 43 other prominent writers, and created works in support of the war effort.

His 1953 novel, Hana no Shogai (花の生涯) about the life of Bakumatsu period official Ii Naosuke was adapted for television as the first NHK taiga drama.

However, from 1966, the increasing deterioration of his eyesight led to near blindness, and Funahashi resorted to dictation in order to continue his literary activities.