In case you didn't know Japanese summers are really hot.
Summers in Japan are much hotter than Paris or New York. They are even hotter than Bermuda or Fiji, where people wear shorts and alohas as business attire. In fact, Japanese summers are as hot as Honolulu.
Honolulu's summers aren't as brutal as Japan's thanks to the breeze and lower humidity.
By the way, the origin of Hawaiian Aloha shirts was said to be a western style shirts made from Japanese Yukata (kimono) fabric.