Whilst he was climbing a telephone pole, he had been pierced by the Bow and Arrow thanks to Yoshihiro Kira, resulting in a hole in his left cheek and the birth of his Stand, Boy II Man.
He asks Rohan Kishibe if he would like to place janken (rock, paper, scissors), but is turned down. When Rohan goes for a taxi, Ken challenges him to janken, to see who gets the taxi ride. After Rohan wins, he gets the taxi. Later at a restaurant, Ken takes an empty table and makes a scene. After winning another janken game, Rohan kicks him out. At the library, Ken challenges Rohan for a book about plants, but the mangaka punches the janken boy. However, Rohan tells his rival he is victorious as Heaven's Door is sucked into his cheek.
However, Rohan turns Ken into a book to write "I cannot attack Rohan Kishibe" on him then separates him. Rohan learns that Ken's Stand can steal energy from his victims if he wins against them, then suddenly, Ooyanagi changes the words so he can attack. Ken places Rohan's arm under his control and since janken consists of five rounds, the mangaka attempts a fourth round, but loses when Ken uses paper to strangle rock.
Now, a third of Heaven's Door is stolen, and Rohan now becomes determined to win. The two jump into the air and throw paper, resulting in a draw. Just as the boy is throwing paper against rock, Ken chooses rock, resulting in another tie.
Ken knows that Rohan would not dare send for help against a kid, and wins the bet. He seemed unfazed after standing proudly on broken glass. On their next janken round, Ken attempts use scissors to cut Rohan's paper, but his hands move to rock suddenly and Heaven's Door returns to Rohan.
To get revenge, Rohan attempts to make Ken resign from janken, but Boy II Man takes Shizuka hostage and demands a rematch. This time, Rohan does win three rounds again. Not wanting to accept defeat, Ken attempts to take his own life by jumping in front of a truck, but Rohan pushes him out of the way. Ken accepts he'll never use his Stand again.