Summer Sonic is one of the biggest music festivals in Japan, if not the biggest. It is held every year, this year on the 18th and 19th of August. I don't know why, possibly because Japan is quite big, but it is held at the same time in two of the major cities; Osaka and Tokyo. It is outdoor and usually has a pretty great line-up! So if you're in Japan for the summer and you still have some money to spend, check out this festival :)!
Summer Sonic Japan
18-08-2018 to 19-08-2018