over all it wasn't bad at all, I did the dub for the first episode and ouch my ears! thankfully sub was so much more friendlier and I was able to comprehend the anime so much better. it wasn't entirely original, I've seen this in a few others now, but, it did have an interesting show of character development, and from what I could take from it, AI like? the attention to details, art wise, was outstanding, and the sounds were remarkable. finally something got the sound of a vibrating phone right! nothing was spared in this one, teen and above will work just fine. a bit of ecchi, such as brief nudity, panty shots... but mild language, a heck of a lot of violence and no drug use other than the "drugs" needed to "hide" from the "enemy".
took me two days to tick it down, so it's not that long, and it ended well, not unlike some stuff that just goes poof, or an ultimate cliff hanger, it will leave you with a few questions however, but I felt the anime, over all, did good for the mere 12 episode job it had going for itself. so, if you're into creatures, science, medicine, creature horror, then might want to give this one a try.
however, the only setback I found with it was, the waste of fillers. there was no need for stock footage of the same old death scenes, the main character is haunted, please, enough already. at least find new stock image to run with from time to time.