Sound Heard Sometime In the Past - S1.E5

With the information from Kumagami as a hint, the student council members continue a stakeout in the middle of the mountains where a wielder of a special ability supposedly hangs out. As they spend their time barbecuing and fishing, Yu comes across the music of ZHIEND through Tomori's music player. And, the one that appeared in front of them as they continued the stakeout...