Ura Butou Satsujin Arc
Though we get a glimpse of Joker in the early chapters of volume 8, we first meet him a couple of chapters later during Recca and Tokiya's match against Uruha Oto's Neon and Miki. He got to play a ladies' man when he saved Menou from falling rocks caused by Neon's final Requiem attack. After that, he showed up on a couple of Hokage's tournament matches, once as a spectator (Hokage vs Saakasu) and once offering the Hokage some tips and information like what he did in Koganei's match against Uruha Ma's Tsukishiro.
Prior to the final match between the Hokage and the Uruha Kurenai, he appeared when Koganei and Saicho came upon J-Keeper while they were roaming around the tournament grounds. In the guise of helping them, he teamed up with Koganei and Saicho to defeat J-Keeper. But on the last moment, he striked Saicho down bringing him to a coma with the intention of angering Koganei and making him fight seriously in the Ura Butou Satsujin finals. Then, he single-handedly defeated J-Keeper with his madougu, Taishaku Kaiten.
In the Ura Butou Satsujin finals, Kurei finally revelaed his trump card, Joker. Joker was the fifth member of Uruha Kurenai and he was pitted to fight against Koganei. The fight between the two ran differently between the anime and the manga. In the anime, Joker instantly concedes defeat even before the match started in order for Kurei to fight, thus leaving fans bewildered on his role and his madougu's power. In the manga, on the other hand, we see one of the best matches in the tournament: Joker vs Koganei. Taishaku Kaiten vs Kougan Anki. Gravity vs Metal. The match between the two lasted for 38 minutes and 14 seconds and it ended with Joker conceding his defeat after being badly injured by Koganei's Kougan Anki's sixth form, Mu. Though he conceded the match, he said that it doesn't mean that he can't fight Koganei any longer since he still has the capacity to continue fighting him.