Athletic Mato is excited to start middle school and meet new people, including Yomi, an artistic girl who doesn't open up easily to others. While awkward around each other at first, things change when the girls discover their mutual obsession for a fantastical picture book. But just as the pair becomes fast friends, they're torn apart by a cruel, wheelchair-bound girl who considers Yomi her personal possession and refuses to let anyone else near her. What's worse, Mato has recently begun to have strange dreams about girls brawling in bizarre colorful worlds that seem to parallel her personal struggles. With jealousy, insecurity, and foreboding dreams always getting in the way, can the two girls ever become true friends?
Vividred Operation is brighter and more lighthearted than Black Rock Shooter, but both come heavy on the meaning of friendship theme, as well as featuring young girls with big superpowers. If you believe in yourself and your friends, you can conquer the world!
They both deal with supernatural dreamlike worlds that can influence the real world and the emotions of people, and they do that by creating a very enigmatic and mysterious atmosphere. Weird and cool fights are also something they share. While Yumekui is a bit more shounen-ish and less serious (and it also lacks a proper ending), I think those who got caught by the style and execution of one of these series will recognize the resemblance and like the other the same way.