Double Black. One of the most devastating histories in the DWMA (Death Weapon Meister Academy).

After a huge loss a few years back, the agreement and or partnership was cut off between the Weapon, Chuuya Nakahara, and the Meister, Osamu Dazai.

Osamu Dazai now works as a teacher at the DWMA while Nakahara Chuuya is sealed somewhere in the school, forever locked in his weapon form.

Who knows if the two will after partner once more.