Chironex Chironex , also known as Kurage in the Japanese version , is a Barian in the " Yu - Gi - Oh ! ZEXAL " anime , belonging to the Fearsome Four of the Dark Dueling World . He is the self - proclaimed best WATER Duelist . Design . Appearance . In his human form , Chironex appears as a tall man with long , sharp nails and long white hair . He wears a suit consisting of white pants , a striped , frilled red shirt , a tattered purple vest with a pink cape and a purple fedora . In his Barian form , Chironex has turquoise skin and purple lips ( which makes him , along with Heartland , the only Barian to have a moving mouth ) . His fedora and hair transform to resemble the bell and tentacles of a jellyfish , respectively , with some of the tentacles hanging in front of his face . He also possesses brown armor and has a red crystal just below his chest . His jellyfish motif makes him the only member of the Fearsome Four not to be based on an insect , but jellyfish are seen as pests in the same way as the others . Personality . Chironex is arrogant , calling himself the greatest WATER Duelist . He also believes that the jellyfish is the greatest predator in the ocean . Due to the aforementioned belief , Chironex prefers to be addressed as " senpai " ( 先輩 ; Senior in Japanese ) and refers to his opponents as " kōhai " ( 後輩 , junior in Japanese ) . When angered , Chironex ' s speech becomes extremely slurred ( In the dub , he simply insults Shark ' s skill as a Duelist ) . He is extremely passionate about WATER monsters , to the point that he insulted Shark for playing " Skull Kraken " , as while it is an aquatic creature , it is a DARK monster . Abilities . Chironex has the ability to turn to and from his original form , a jellyfish . In his human form , he can extend tentacles from his sleeves to poison his foes . He also has the ability to appear and disappear at will , as well as turn invisible . When walking , Chironex ' s footsteps generate a small amount of water . Etymology . " Kurage " means " jellyfish " . " Chironex " is derived from " " " " , the scientific name of the sea wasp ( a species of ) which is the most venomous animal in the world . Biography . History . Chironex was once the mentor of Mr . Heartland . An underworld Dueling criminal , he was involved in a car accident while fleeing from the police . The accident resulted in the deaths of him and the entire Kastle family . Chironex was eventually reincarnated as a Barian . Yu - Gi - Oh ! ZEXAL II . Chironex was one of the Fearsome Four of the Dark Dueling World . He was sent to Earth with the other members to gather the " Numbers " by Vector . After Erazor ' s defeat at the hands of Yuma Tsukumo and Trey , Vector ordered Mr . Heartland to send Chironex after Shark , as both were WATER Duelists . To this end , Chironex infiltrated the hospital where Shark ' s sister Rio was staying . He infected her with jellyfish poison in order to lure out Shark . He cornered him at his old house and infected him as well , wagering the antidote on a Duel and musing that Shark looked familiar . They were interrupted by Quattro , who joined the Duel on Shark ' s side , with Chironex having 8000 Life Points and both Shark and Quattro having 2000 . Chironex brought out " " , inflicting 1600 damage to Shark . Quattro countered with " " . With aide of Quattro ' s " Celestial Strings " , Shark was able to defeat Chironex with " " . Quattro proceeded to take his " Number " , while Chironex recalled that Shark was in the car that he crashed into years ago and then shockingly stated that since he was the only survivor , that Shark couldn ' t be standing before him right now . Deck . Chironex uses a " Jellyfish - themed WATER " Deck , primarily focused on swarm and burn tactics , centered around " " and " Kragen Spawn s " .