Nanase's pony tail makes an appearance in Sayonara No Imi -- the meaning of good-bye. They all graduate. They will all graduate.
Nanamin's last song with Nogizaka, and the final graduation from 2016 although she did not truly graduate until the 5th Year Birthday Live in 2017. Nanamin was one of two members to have been in the fukujin for her entire Nogi career. The fukujin are the gods of fortune in Nogi, the top 7+ of the group. She was always one. She left on top. Shiraishi is the other.
This song is too sad, and I can't really listen to it too much as Nanamin's graduation is too much. Sayonara.