if your looking for short clips of iv idols (particularly Rei Kuromiya), just frequently visit the Idol Video Clips/Downloads. https://www.akiba-online.com/forums/idol-video-clip-downloads.57/
but i do prefer Rei's sister Aya Kuromiya more, with the CT shots she provides.
try this other site:
http://u15x.com/?s=rei+kuromiya
i tested download short clip (via UpStore) the file seems to still up.