For people being interested in it, her Japanese fans have decided what to sing as encore surprise for Kuu on the Kawasaki dates.
On Instagram:
https://www.instagram.com/p/B2RKhbSH_OP/
On Twitter:
https://twitter.com/m_taka5000/statu...73643291971585
And for the Fukuoka dates:
https://twitter.com/seiko228kumi/sta...07213058326528
But usually they also make announcements at the venue and/or give out flyers with the song and the part of the lyrics they gonna sing.
They decide which songs to sing with polls on Twitter, if someone wanna take part in it (アンサプ is the short word for it in Japanese).