This series is actually a sequel (spinoff really) to the "428: F'sa Sareta Shibuya de" visual novel for Wii. The viewer follows friends Canaan and Maria for most of the series. The series is reminiscent of a Resident Evil style plot where some entity has purposefully infected people with a rare virus. The virus is almost always lethal, but there are those rare people who actually survive the virus but have their bodies affected in strange ways. Canaan is one of the people. Maria is her photographer friend. Though it is unnecessary to know what happens in the previous visual novel, it does help to explain some of the early plot holes and explain how Maria and Canaan know each other. Some of this is revealed in flashbacks through the anime series.
The series is short, only 13 episodes, but most of the episodes have a lot going on. The animation is very high quality and the backgrounds are lusciously beautiful. The Japanese voice acting is stellar. I watched both versions, and I have to say that Yum Yum and Maria in particular are nearly perfectly matched with their Japanese voice actors.
My negative points are few, but they are important. First, due to the short length of the series, there are quite a few plot holes and plot threads left unfinished. But probably the most annoying is a little 'glitch' in episode 8. The subtitles actually hit one off. Basically when someone is speaking, the subtitle for the next persons' audio is shown. So you see Canaan ask one of the girls if she is okay "Daijoubu ka?" but the subtitle says "Honored Alphard". Then we see the next scene Cumming's says "Alphard sama" with the subtitle for the next dialogue... awkward! But this is only in episode 8. Kind of makes you wonder if Sentai actually watched the finished Japanese audio and English subtitle version for error proofing.
The only other negative point is the finale kind of seems rushed and then we see one particular character having a very drawn out and melodramatic breakdown. I understand it is in keeping with her character, but I might not be the only person who was thinking "Hurry up and die already! I'm sick of hearing you! Jeez!" But I can totally forgive these small annoyances.
I actually checked this out from my local library, so I am quite pleased with it overall; but had I paid $42 I would probably be a bit miffed. Though it is a good series, it is short, and it's not too necessary to own. If you can stream this online or rent from Netflix or your local library (if you're lucky enough to have an anime friendly library nearby), then I would recommend that course of action before spending $42 to buy it.