TOKYO, Sept 23 (Reuters) - Japan’s government and central bank must work closely together to avoid triggering an unwelcome yen fall caused by a loss of market trust over the country’s finances, Taro Kono, a key contender in the ruling party leadership race, said on Thursday. “If market trust over Japan’s finances is lost, that could trigger a yen fall,” Kono said. “If yen falls proceed, import costs would rise and cause inflation,” he said in an online debate among the candidates in the race. (Reporting by Leika Kihara; Editing by Giles Elgood)