Sigma is a member of the terrorist organization the Decay of Angels. Sigma is the quiet and gullible manager for the group and is often pranked or used by his colleagues. One day Sigma is helping his superior, Fyodor Dostoevsky, with a jail break. During this jail break Sigma turns his back on Fyodor and instead helps Osamu Dazai, the man being framed by Fyodor. Sigma helps Dazai with his jail break instead, showing Sigma values his morals more than his relationships.