Barian and Human (past life)
Nasch is originally the leader of the Seven Barian Emperors from the Barian World until his death in the Yu-Gi-Oh! ZEXAL anime. Reginald Kastle was actually Nasch who ended up on Earth after he died, and took back his position as the leader of Seven Barian Emperors after reincarnated, later in Yu-Gi-Oh! ZEXAL anime.
In the shaded image, his hair could be seen which are similar to of Reginald Kastle.
Until his death, Nasch was once lived life as a human - king of the United Lands of the Poseidon Ocean alongside his sister, Marin. A number of years later, Nasch was reincarnated as a Barian, with no memory of his previous life like all Barian Emperors. He became leader of the Seven Barian Emperors, joining up with the other six and plotting to destroy the Astral World. Both Nasch and Merag were later killed by Vector. Dumon inheriting the control of the group and thinks the two simply vanished.
Yu-Gi-Oh! ZEXAL IIEdit
Later on, both Nasch and Marin are briefly mentioned by Vector stating that they had vanished from their world one day and that they might be on Earth as well. Vector also tells Dumon that on Earth he may be able to pick up on on Nasch's scent. Prior to his disappearance, it is implied that he was the one leading the Barian Emperors, as Dumon laments on how he would think of the current situation at hand. Don Thousand, however, states Vector to have killed Nasch and Merag.
After the duel between Shark and Abyss, Dumon and Astral were able to see Shark's previous life which confirming that Shark and Rio were respectively Nasch and Marin. Dumon later approached Shark and Rio shows to Shark past life that he is one of the Seven Barian Emperors, Nasch. Shark continues living through Nasch's memories, where he looks after the orphaned girl, Iris, as he goes into battle against Vector. There, Shark is contacted by Rio's spirit, who reminds him his fate is his own to make. Going on his own to face up against Vector, Nasch arrives at the labyrinth he visited before and confronts him in a Shadow Game using stone tablets. Vector deals a lot of damage to Nasch with his Gorgonic Guardians, but Nasch manages to summon Abyss Splash and defeat him. After the duel, however, Nasch discovers his men, along with Iris, had all been killed as a result of the shadow game, their souls ascending to Barian World and later chose Shark as the leader of the Barian World. Having seen all of this, Shark comes to accept the truth that he is Nasch, bitterly realizing that Yuma Tsukumo, Astral, and Kite Tenjo would soon become his enemies.