don't get the 100yen collapsible umbrella, its small and with a little gust of wind it gets easily damage, get the 300-500yen one they are sturdier..
my friend went to hokkaido last summer and even on the pick of summer it was cooler there around 15C, just like spring in osaka.
Summer in Japan, especially in Kansai area is really HELL and that is coming from someone who live in a tropical country all her life. Last year was the hottest I've experienced so far, I hope it would not be as hot this year.
Just be sure to get a sunscreen and some vitamin C. Airconditioning is mandated to be 24C by the goverment so don't expect cooler temperature inside dept.. get a fan too
