So, to go to Japan in June, the clothes to be prepared are:
1.
Long sleeve shirt,
2.
Short sleeve shirt,
3.
T-shirts,
4.
Jeans,
5.
Casual shoes,
6.
Wear a sun hat.
-
note:
In public places in Japan, no matter how hot the weather is, you can't wear a shirt instead of a vest.
Because, sweat soaked the shirt, you will accidentally rub it on others on the bus, which will be very annoying.
Therefore, Japanese people usually consciously wear a T-shirt under their shirts.