Events this week will determine whether the yen has a record fourth annual decline in 2015, or is the year's best-performing major currency.
With just days left, the currency has slipped 0.5 percent versus the dollar this year. That makes it the second-best performer among 16 major currencies against the greenback, behind the top-ranked Swiss franc, which has strengthened 0.8 percent. The yen advanced for four straight days through Friday amid declines in Japanese stocks.
"There's the potential for more yen buying amid continued risk aversion," Toshiya Yamauchi, a senior analyst in Tokyo at Ueda Harlow Ltd., a margin-trading services provider, wrote in a note to clients. "If the market turns, it will not only derail a record fourth annual decline for the yen, the start of 2016 could be the beginning of three years of weakness for the dollar."