Akane Hiyama
About
Akane is absolutely without a doubt a pure genuine Yandere, although she seemed like an innocent girl when she first was shown in the series. She is not afraid to attack those whom seek a relationship towards Seiji, and would most likely kill them if needed. It is proven that she would kill people in episode one, when she kept stabbing Seiji but he couldn't die because Guri said that they were short-termed angels.
She also is willing to kill herself when Seiji died in episode five.