Sōsuke Aizen
Character songs are not restricted to anime protagonists. Antagonists such as Zechs Merquise, Master Asia, Sailor Galaxia, and some of the villains (such as Devimon and Sōsuke Aizen) also have their own character songs. In some cases, these are regarded as more interesting than those of the protagonists as they often provide the only glimpse into a villain's character.