Katsu appeared in three movies in 1954 and, due to the popularity of jidai-geki (period dramas), acted in another ten films from 1955 to 1958. One of these films, Kan Kan Mushi wa Utau (1955), also featured the stunning Tamao Nakamura. Here the future Mr. and Mrs. Katsu met and acted together for the first time.
In 1956, Katsu first appeared in color in the motion pictures Tsukigata Hanpeita: Hana no Maki and Arashi no Maki, both directed by Teinosuke Kinugasa. Katsu continued to play minor rolls alongside then top Daiei stars Kazuo Hasegawa and Raizo Ichikawa throughout 1956-57. Then in 1958, at the age of 27, Katsu took a step up the movie star ladder with larger roles in Daiei’s first Vista Vision movie, Yukyou Gonin Otoko, and first all-star Cinemascope feature, Chushingura (Loyal 47 Ronin). In contrast to his high standing in the flamboyant Nagauta/Kabuki community, Katsu’s popularity in movies at this time was still somewhat less than phenomenal. However, he continued to work steadily, appearing in over 10 movies in 1959 alone.
With 1960 came Katsu's first leading roll in Gentaro Bune, directed by Kunio Watanabe. Katsu negotiated with Daiei to have the female lead, the wife of his protagonist character, played by Tamao Nakamura. The two had already been in ten films since 1955, but this picture offered their first opportunity to act as a husband and wife.
While Shintaro and Tamao were by now something of an item, and Tamao was no doubt pleased with the idea of appearing as the wife of her boyfriend, she was not as enthusiastic about the project itself; Gentaro Bune was a rather low budget, black and white affair, not the kind of film an up-and-coming actress would normally jump at. Nevertheless, Tamao wound up co-starring with Katsu in the picture.
Just as Kabuki and Nagauta had kept their important relationship for centuries, so Katsu and Tamao had come together as if fated to. To the Japanese movie industry of their day, they were the ultimate movie star couple, Japan's very own Dick and Liz. They were attractive, talented, appeared in films together and embodied the glamor and excitement of the modern Japanese cinema. Throughout the years, Tamao weathered many ordeals as a result of her husband's outrageous life style, yet throughout it all she remained a loyal and loving wife, until the day of his death. Shortly thereafter she famously stated, “If I were born again, I would certainly marry Katsu again.”