Alias: Papillon (パピヨン)

Known relatives: Jirou (younger brother), Bakushaku (great great grandfather)

Weapon: Busou Renkin named "Near Death Happiness"

Koushaku Chouno is a major antagonist in the Busou Renkin series. He is introduced very early in the plot and is the main villain working against Kazuki Muto and Tokiko Tsumura up until the L.X.E. is introduced.

He appears sinister and sickly, described as having "eyes like rotten river sewage." He aspires for eternal life, no matter which method he must use to attain it. This huge desire for immortality stems from his affliction by a mysterious disease that weakens his body drastically.