Shares of Yokohama Rubber have more than doubled since January, making it one of the Nikkei's hottest stocks.
While some particularly successful outliers have boosted the Nikkei's average, the index is up a whopping 34% this year.
Over the same time period, the Shanghai Composite is down 3% and the Hang Seng has declined 1%. The Australia ASX All Ordinaries is up 9%.
Japanese Finance Minister Taro Aso has defended his country's fight against deflation, saying the yen's decline is an unintended consequence.