No major spoilers... yay!
Kiznaiver was an okay anime. It has a pretty short but slow story that I think focuses on character development a bit too much. I loved the character design for the main characters, and the sound was okay. With the first tag being drama, you can expect it to have a lot of drama, but the drama only starts towards the end. It also lists sci-fi and psychological as genres, but there wasn't as much of those as other anime. So I guess you can say that Kiznaiver is 90% drama.
The story is a really good and original idea. The being able to feel each other's pain thing really makes it different from other anime I've watched, and I could not see how the story would be like without it.
However, the story is slow. The first half is just about them becoming friends and doing stuff together. Kind of boring. It is only until the second half when we start to learn more about the characters, and when problems are introduced.
I loved the special character design for the main characters in this anime, especially for Tenga and Nico. Other than that, the animation and sound are okay, not too good or too bad.
Kiznaiver focuses on the relationship development a lot. After being forced to become close friends, the story is about how their friendships suffer, and how they get back together. There is also a lot of one-way romances/crushes, which are kind of frustrating but nice to see.
However, the characters have very different but simple personalities, and you get kind of bored of their personalities in the end. The characters themselves don't develop in the story, and you don't still don't know much about anybody in the end, except for Katsuhira and Nori.