The live stream will be done on Summer Sonic’s official YouTube channel. There is no mention of specific artists. They do mention it’s a world-wide stream, and that all 4 stages (MARINE, MOUNTAIN, SONIC and RAINBOW) at Summer Sonic Tokyo will be broadcast over the 3 days. Osaka will not be broadcast.
BABYMETAL plays on the MOUNTAIN Stage in Osaka on Friday, August 16th at 18:50 and in Tokyo on Saturday, 17th at 19:00.