Kaijuu Girls: Ultra Kaijuu Gijinka Keikaku

Japanese Title: 怪獣娘[かいじゅうがーるず] ~ウルトラ怪獣擬人化計画~

Plot
Humanity's battle of many years with the kaiju, giant monsters, has finally come to an end. Now that Earth has entered an age of peace, girls with the souls of kaiju have begun to appear, giving them the ability to transform into kaiju. They are known as the Kaiju Girls, and this is the powerful, transient, beautiful, and at times easygoing story of the strange fate these girls bear.