|“||Hey mister. Wanna play rock-paper-scissors?||”|
Ken Oyanagi (大柳 賢 Oyanagi Ken) is a minor antagonist appearing in Diamond Is Unbreakable.
Ken is a young boy of short stature, slim build and medium straight hair. His attire consists of a headband, open ankle-high sandals and shortalls with both straps on one shoulder; the garment is adorned on all sides by several large safety pins.
On his left cheek, is a large hole produced after being impaled with the Bow and Arrow.
Ken's wish is to become an adult who is respected just as much as Rohan. He has no real knowledge of Stands at the start, but he quickly learns more as the match progresses. He is decisive in his actions, willing to sacrifice himself after being defeated and taking a baby hostage to get another match against Rohan. He heavily believes that luck is on his side. Rohan describes him as a typical bouncy kid with an ordinary life and no family problems upon using Heaven's Door on him.
- Main article: Boy II Man
Boy II Man is a Stand who enables Ken to steal someone's Stand when the latter participates in a game of rock-paper-scissors 5 rounds long with him and loses. Each round lost causes the victim to lose a third of their power to Ken. An ultimate win from the victim's part gives back the full Stand.
Diamond Is Unbreakable
Ken fell off a telephone pole, resulting in a hole in his left cheek. This hole was likely caused by the Stand-creating Arrow that Yoshihiro Kira used to create new Stand users in Morioh. Being a huge janken (Rock Paper Scissors) fan, he challenges famous mangaka Rohan Kishibe after running into him. Rohan, very annoyed by his presence, uses Heaven's Door to cheat and chase him away, but Ken appears again, and Rohan plays a game in the hopes that if Ken wins, he will leave him alone.
However, Ken's main intention was to win over Rohan's "mind power" by defeating him in janken, as he believes it means he would surpass him as a person as well. When he finally wins after several defeats, his Stand absorbs a little of Rohan's Stand power and starts to learn about Stands. He is tricked by Rohan in their last match, who teaches him how to surpass himself and turn luck to his side instead of just relying on it. Thinking it was unfair, he takes Shizuka hostage and Rohan agrees to battle him again, but, this time, Ken is defeated fair and square.
Not accepting his defeat, he throws himself in front of a truck, but Rohan jumps with him and both are almost ran over. The truck driver misses after accidentally having his vision blocked by Yoshihiro Kira. Seeing that luck is really on Rohan's side, Ken admits defeat. Rohan then says he likes Ken because he can take decisive actions.
- According to Heaven's Door, Ken reads Shōnen Jump every week and is in 6th grade at his school. He loves soccer but played baseball until his coach complained about his long hair and he was forced to quit (while blowing nose on the coach's hat). He also hates peppers and anpan, likes fatty cuts of meat, is afraid of the dentist and Namahage, and has never used a public restroom. He also has no family issues.
- During the climax of his fight with Rohan Kishibe, Ken said "Good!", a clear reference to Daniel J. D'Arby.