He is a traveling dancer who accompanies Kokonoe. Two years before the start of the series, a man resembling Sousuke destroys his village and kills his family. When he first meets Sousuke, he attacks him thinking he is the person who attacked his village. He looks a lot like a woman but is quite strong that even Shino remarked on it.
Kobungo once had a crush on him without knowing he was a man.
Two years ago, he was attacked by Ao, Sousuke's shadow. Ao took Keno's heart and left, but surprisingly, Keno still survived until Kokonoe came. Kokonoe took interest on Keno's strange condition, and she gave her heart to Keno.
Since then he had continued to pursue 'this man who took everything from him'.