Anticipating the cool aesthetic of Seijun Suzuki's Branded to Kill and based on a crime novel by Shinji Fujiwara, the author of the original material for the same year's A Colt is My Passport, A Certain Killer and A Killer's Key are similarly stylish contemporary hitman thrillers directed by Daiei's top director of jidai-geki, Kazuo Mori (The Tale of Zatoichi Continues) and starring the studio's top actor Raizō Ichikawa (Shinobi: Band of Assassins, Sleepy Eyes of Death).

In A Certain Killer, Shiozaki's low-profile existence as a chef at a local sushi restaurant serves as a front for his true job as a professional assassin whose modus operandi is poisoned needles. He's approached by Maeda, a low-ranking member of a local yakuza group, to take out a rival gang boss. But the sudden arrival into his life of a spirited young woman, Keiko (Yumiko Nogawa, Gate of Flesh), has dramatic ramifications on his relationship with his new employer. Ichikawa's lone wolf assassin is back in A Killer's Key, this time masquerading as a traditional dance instructor named Nitta who is called in to avert a potential financial scandal that threatens to engulf a powerful yakuza group with ties to powerful figures in the political establishment.

Co-scripted by the director Yasuzō Masumura (Giants and Toys, Blind Beast) and featuring masterful scope cinematography with an expressionistic eye for colour by one of Japan's most esteemed cinematographers, Kazuo Miyagawa (Rashomon, Ugetsu).