Koda has slanted eyes, reddish-brown hair in dreadlocks, with the lighter colored sides shaved. He is usually seen wearing his red and orange track uniform, along with a track jacket.
As a demon, he becomes a large bull-like creature with a huge mouth and horns. His human face is placed on the forehead of the demon, and it gains serrated teeth following his siding with the demons.
Koda was committed to track and field and remained distant to those around him at events. After Junichi died this deteriorated Koda's frame of mind and he was periodically affected by deep bouts of grief.
Koda is shown early in the series, being interviewed regarding the murder of one of his track teammates. At some point he was possessed by a demon, and both his appearance and personality is said to have changed. His performance in track greatly improved and he set five youth records, considered a "super high-schooler."
He was in love with one of his teammates and childhood friends, Junichi, who he kills under the influence of his demon. This occurs sometime before the first episode and brings him extreme mental and emotional turmoil.
Ryo Asuka discovers his possession and plans to expose him, alongside the truth of demons, to the world at Koshien Track and Field. Ryo gives him water that causes him to transform after footage from Sabbath is broadcasted. Demon Koda tramples and gores several athletes in the arena before escaping to the parking lot. He is then confronted by Akira Fudo, who insists to Koda that he is a Devilman and carries him off to save him.
He is taken to a rooftop where he must stay in secret, as Akira lied to Ryo about killing him and the world knows he is a demon. Miki Kuroda runs into him accidentally, and they discover they are both Devilmen. They take part in practice races together. He expresses that he no longer cares about whether humans or demons win the war, and wishes it would end quickly as he would benefit either way. Miko comments on his selfishness.
With the demons set to win, he eventually sides with them and attacks Akira as he tries to defend humans, albeit ones who were prepared to stone those they thought were devilmen. Akira defends himself by instantly tearing him in half during the final battle.
- Koda's Devilman design may of been inspired by the Devilman Lady demon leader Vlava, though this is entirely speculative.