It centers on Kamo and his partner Tora, who work in the underworld as "avengers for hire," taking on jobs from the victims of violent crimes and families seeking vengeance for wrongs done to them. (Source: mangaupdates.com) ~~ Adapted from the manga series "Gedo no Uta" (外道の歌) by Watanabe Daisuke (渡邊ダイスケ).