This photo was uploaded on Twitter.
It’s taken at the world’s largest dōjinshi fair “Comiket” (コミケット), also known as “the Comic Market” which is held twice a year in Tokyo.
But it seems like it’s not the cosplayer’s clothes that are of the biggest interest by the photographers… rather what’s under it. (?)
I guess this is a moment where you can say “Only in Japan…”