The thigh-length hair girl is named Bandou Kanon and was born in 2000. She was 17 years old in the above videos. See

jpop.fandom.com/wiki/Bandou_Kanon

jpop.fandom.com/wiki/Milky_Berry

I love it when women flip and toss their long hair around while dancing! A "hair swoosh" adds so much energy to the moves. (Are those correct english terms?)