While he attended Toyo University to study photography he met Kōki Mitani, a script writer for radio and playwright who aspired to be an actor and who turned his attention to the theatre.

In 1983, Nishimura, Mitani and others including the actors Zen Kajiwara and Kazuyuki Aijima formed the Tokyo Sunshine Boys, a comedy troupe that grew in popularity over the following ten years.

They produced the popular play 12 Gentle Japanese, a parody of Reginald Rose's 12 Angry Men.

In the 1990s the success of the Tokyo Sunshine Boys brought Nishimura parts in television dramas, notably a part in Furikaereba Yatsuga Iru and as the flamboyant Shintaro Imaizumi in Kōki Mitani's Furuhata Ninzaburo.

The Tokyo Sunshine Boys disbanded in 1998, but most of its actors, including Nishimura, continued to work in television.