Back Stairways (1965)

A young man named Kijima who works as a pianist in a small bar is surprised when one of the customers asks if he won't pretend to be the fiance of his sister. He is even more surprised when he is offered a million yen to play this apparently harmless role. Actually, it is anything but harmless. Both the customer and his sister are involved in a jewel robbery in which they have double-crossed two of their accomplices who are now out of prison and thirsting for revenge.