Ryoga Kamishiro (神代凌牙, Kamishiro Ryōga), nicknamed Shark is a character in the spin-off manga Yu-Gi-Oh! D Team ZEXAL. This is an alternate incarnation of Reginald Kastle, a character from the Yu-Gi-Oh! ZEXAL anime. He is a delinquent who leads Team Shark.
Tokunosuke wanted to enter Shark's Dueling Team, but Shark said he'd only accept Tokunosuke if he defeated the leader of Team ZEXAL, Yuma Tsukumo. However, Tokunosuke failed to do so, and rushes up, but he is despised by Shark's Team.
Shark called Team ZEXAL weak, and then challenged Yuma to a Duel under some conditions: betting their teams' badges, which symbolizes the pride of the team; and second, if Yuma lost, Tokunosuke would enter Shark's team as a slave. With no other option, Yuma accepted the Duel.
Astral instructed Yuma on how to Duel, but Yuma didn't listen to him, which led to his eventual loss. However, when Shark attempted to take his badge, he saw Yuma's cards, and noted that he could have won. Because of that, Shark declared the dispute as invalid, and told Yuma that the next time they Dueled, he'd use his true strength.
Shark uses a WATER Deck centred around Xyz Summoning easily through cards such as "Big Whale" and "Shark Stickers". He also utilizes several cards to weaken his opponent's monsters, such as "Shocktopus" "Black Ray Lancer" and "Forbidden Chalice". Shark later uses cards such as "Saber Shark" to allow him to access higher Ranked Xyz Monsters such as "Number 73: Abyss Splash". In addition to this, he utilizes "Number 101: Silent Honor ARK" along with "Rank-Up-Magic Barian's Force" to Special Summon "Number C101: Silent Honor DARK" which he uses alongside cards such as "Black and White Wave".