Aru koroshiya no kagi (1967) - it's very easy to confuse this film for another film Aru koroshi ya (1967) by the same director, with the English title variously and often wrogly transposed from one to the other - one is "A Certain Killer's Key" and the other is "A Killer's Key" and one is a sequel to the other, and it's super confusing. I went with the most usual title for this film in English: A Killer's Key. In any case, in this film [SPOILERS ALERT!] the contract killer is a traditional dance teacher.

I love early Japanese B films, and here we have a marvelous example. The colors are amazing, the locations fantastic, and has some really nice acting from all involved, particularly the young geisha learning dance from the assassin teacher. The contrast of the Western inspired music to the very Japanese settings is fantastic too. The plot is somewhat silly and hardly original, but as often with these B movies, it's not the point of the movie. It's all atmospheres, and it's outstanding for the mood. Highly recommended!