In Japanese, tag is called "oni gokko" (鬼ごっこ). This weekend, approximately 1700 played the game at a stadium in Tokorozawa, Japan.
The fifty oni (demon) were "it" and wore red tights so they'd be easy to identify. There were referees, and once you got tagged, you were out.
The event was held by New Balance. You can see some of the festivities in the video below, courtesy of NHK.
This is not the largest recorded game of tag. In 2013, 2202 students from Elkhart Community Schools in Indiana claimed that honour.
１７００人が「鬼ごっこ」 埼玉 [NHK]