SACHIKO'S WEDDING By Clive Collins (Marion Boyers: $21.95; 256 pp.) . We meet Sachiko, a young Japanese woman, on the day she is being married to Mr. Ueno, a man she hardly knows and certainly isn't in love with. Sachiko had fallen into a series of masochistic affairs--with an old professor she has idolized, with a married sadist who beats her, with a kindly but incredibly dull hairdresser from a lower class. But her parents, increasingly angry that she had not married, introduced her to a series of mates, all of whom Sachiko spurns. Her happiness is her work: She translates romance novels from English and sets up a simple life alone. Sachiko's lonely odyssey personifies a culture that still has no place for women in it other than as daughters, wives, mothers. Clive Collins' brisk story is a fascinating glimpse into a modern culture built on ancient traditions.