Dazai Osamu is based on a Japanese author by same name. His ability No longer human is also based on Dazai Osamu's popular Japanese novel by same name.

Kamina is a young man from Jiiha village who dreams of leaving the village and go to the surface, which he saw as a kid. He's very passionate about his goals, expressing his wishes through energetic speeches, which seems to affect all those who hear him. He convinces Simon to help him with his plan to drill through the roof of the village and get to the world above, but the plan failed and he was put in prison. He left the village shortly thereafter with the help of Simon and a young girl named Yoko, as a result of fighting a Gunmen, who broke into the village from the surface. After he, Simon, and Yoko break through, they meet many enemies and friends as they go, to the point of building up a resistance force, the Gurren Brigade to fight in their war against the Beastmen Empire who hunt on human beings who live on surface, and becoming their leader. (Source: Wikipedia)