Haters gonna hate.
The first twenty-five minutes were a little boring when I was watching - okay, some cute moments between friends, and random symbolic moments with BRS and Dead Master. Repetitive. But it wasn't until later when I realized how absolutely valuable every one of those twenty-five minutes was, establishing the bond between Mato and Yomi, how important getting Yomi back becomes to Mato. And, of course, building suspense. The tension when Mato discovers Yomi's gone. The tension with Mato and...herself.
Interestingly, BRS and Dead Master are supposed to be their other selves, and you see within each girl the opposite of herself exists. Mato is an excitable, tomboyish girl - but BRS is calm, collected, rational (and badass). Yomi is sweet and polite and adult-like, but Dead Master is showy, evil, and completely insane. That face she has when BRS makes the climax confirms it. She can't accept any form of affection; the only way to get Yomi back is to destroy that inner self completely.
Of course there are open ends left; how did Yomi merge with her other self? What's wrong with Yuu? But I don't think there's a sequel to remedy these. (Do you have any idea how much work they had to put into this thing?) These open ends are intentional, made to make one think.
The open end that I don't think was intentional was Black*Gold Saw. If BRS is fighting her, that means Mato knows her counterpart somewhere, but said counterpart did not even get mentioned. As for STR, I think she's Yuu. STR's figure was approaching while BRS and Dead Master were duking it out, and Yuu's feeling of being "left out" is increasing. Once again, probably not a sequel, although I have this image of BRS and a reformed-type Dead Master (not DM herself, she's dead) fighting against STR.
The characterizations were stellar. Mato at first appears to be your typical excitable tomboy, but she's definitely a more emotional one. Yomi is a polite, drawn-back girl, but she has signs of jealousy and loneliness, and Yuu of course is more than your average lolicon. Each character has an in-depth, deeply explored personality that's always more than meets the eye.
The scripting was done well. The art was beautiful, down to the in-depthness of the energy blasts and the "special" eyes of the alter-selves. Can't blame them for so much work in 50 minutes.