Shun Kageyama operated as Kamen Rider TheBee, acquiring the TheBee Zecter after Kagami relinquished it. Prior to it, Kageyama was originally under Yaguruma's command. After TheBee Zecter rejected Yaguruma and chose Kagami, Kageyama attempted to make Kagami understand his new responsibilities. He was baffled when Kagami rejected TheBee Zecter in favour of his friendship with Tendou, whom he developed a grudge against. Becoming the new leader of Shadow, Kageyama turned his back on Yaguruma and used many methods that contradict his former mentor's beliefs. Overtime, Mishima also sees he as being unable to handle the missions assigned to him. Eventually, he is defeated by a vengeful Yaguruma who relieved him of the TheBee Zecter which ended up in Tendou's possession. No longer qualified as TheBee, he was ousted from the Shadow elite. Battered and broken in both body and mind after being facially scarred in the crossfire between Shadow and the Worms, Kageyama is saved by Yaguruma, who once again invites Kageyama to hell, this time giving him his own Hopper Zecter as a present.
Now under Yaguruma's wing, he refers to him as "aniki" (brother). Once their partnership formed, both Kageyama and Yaguruma set out to for revenge against Kabuto by ambushing him and Gatack within an abandoned factory. Unlike Yaguruma, Kageyama is not completely into the darkness yet and Yaguruma often corrects his way of thinking whenever Kageyama shows signs of 'reaching the light'. Yaguruma tells him that his way of thinking is wrong and even the slightest bit of light will destroy them. After discovering the girl Kageyama saved early had become a Worm, the Hoppers annihilate the Worms together, and they manifest in their own power. Kageyama once again questions the value of the light, but Yaguruma tells him that they live in a world of darkness. The two work to destroy a confused and weakened Rena Mamiya. Their attempt almost works, but Rena is saved by Kamen Rider Drake along with Gon, who distracts them, allowing their party to escape. Kageyama later asks Yaguruma why he didn't kill her, and Yaguruma answers by saying that he has indeed taken a liking to her. This led to an infuriated Kageyama, as it went against their beliefs of abandoning the light. Yaguruma is shocked however, when he gets rejected by Rena, and his bond with Kageyama is restored. Kageyama and Yaguruma defeated Tsurugi, and through depressed, Tsurugi is tricked into joining them.
The trio then eventually encounters Reiji Nogi who makes short work of them using "reflect" to use all their Rider Finishers against them. Kageyama wants to help them fight, but Yaguruma laughs at him for trying to be an ally of justice. Kageyama reverts to his old self briefly and picks up the abandoned TheBee Brace, until after being defeated by Reiji Nogi. Ultimately, he becomes PunchHopper again. Kageyama ignores Tendou's request for help, stating that he will not help humans. Kageyama then becomes one of the many looking for the Worm identification necklaces, believing them to be useful in his mission. Upon seeing Kageyama with a Worm identification necklace, Tendou tries retrieving the device but failed. Kageyama tells Yaguruma that he has become a Native and can no longer control himself due to fact that having three Native necklaces sped up his transformation. As a show of pity, Yagruma uses a Rider Kick to end Kageyama's suffering. As Kageyama dies in Yaguruma's arms, Yaguruma mentions that the two will always be partners.