Spring wear

I will be Osaka on 22/4/2016 to 25/4/2016 and weather cool in spring or just wear jacket .

It's a little far out for a weather forecast, but the temps are typically in the low 20s with more than 50% sunny days around that time. I'd mainly wear light pants and a light jacket over short sleeves. More info here:

http://www.japan-guide.com/e/e2273.html

I was in Osaka in early April a couple of years ago. I only wore tshirts and jeans and didn't even use the light cardigan I bought. It did rain a lot though so I recommend a small umbrella or waterproof jacket.