This is track #22 on this CD version. This is mamomo's own YouTube page, so the credits can be trusted. I've added the info.
https://www.youtube.com/watch?v=BeQGLn2GOKk
This is a shortened version of track #21. It's an unofficial upload, but the vocalist is almost certainly nayuta. Can anyone confirm?
https://www.bilibili.com/video/av18382475/