Futhur notes of the characters. Like I said this fic is based a lot on Naruto Shippuden so here are further notes on the main characters
Luffy: I've decided to have Luffy go through a wardrobe change. He would be wearing the same black suit he wore in Strong World except instead of the black overcoat, he would be wearing a green cloak, the exact same coat his father Dragon wears. I felt that if he wears his Strong World suit along with Dragon's cloak, he would look similar to his father. This also makes Luffy look significantly cooler yet darker. Also even though he is based on Sasuke Uchiha, he is not. So no Sharingan or Mangekyou Sharigan. The closest thing he would have to Sharingan would be very powerful observation haki. His arnament hardening would function as Susanoo. He would not be ruthless and bloodthirsty like Sasuke but he would be very nihilist and say things he probably would never say. He would not be overpowered like Sasuke and his main offense would be his gears and haki. Like I said he is inspired by Sasuke, not Sasuke himself.
Nami: Her role is of Naruto. She feels terrible about what she said to her hero and also feels responsible for his dark path. Just like how Luffy saved her from slavery under Arlong, she wishes to save Luffy from his dark path. She is based on Naruto but not Naruto himself well herself or whatever. So she would not have any special power or destined to fight Luffy or anything. She simply wants to save him because she loves him. Expect a lot of angst from her. Luffy himself would make her cry a lot.
Straw Hats: They all feel bad about making Luffy leaving, Nami the worst of all. They all want to save him. However Luffy this time is not above harming and killing his nakama so expect a lot of drama between Luffy and the straw hats.
Dragon: Dragon would be Tobi's or Madara's equivalent. Just like how Tobi used Akatsuki to further his own goals, he used the army to aid his own goals. Also Tobi pretended to be stupid when he is sinister, Dragon also pretended to be righteous when he is evil. Also here Dragon would be the final antagonist and also the Strongest character in the whole story having the storm storm fruit.
One Piece girls: I always felt Luffy could have a harem since he helped so many girls. So all the girls who were directly helped or saved by Luffy would feel terrible about his corruption and wish to save him, just like he did for them. So Vivi, Shirahoshi, Hancock and possibly Conis will make appearances. They too have seen Luffy's corruption and wish to save him just like he did for them. This fic is LuffyxNami but he has helped so many girls that I think they would want to help him back. They also in addition to the crew give Nami strength and support similar to how Naruto got support from his friends. Alabasta, Ryuuga, Amazon Lily and Skypia would have one of the four keys (the remaining 4 in the hands of one Yonko). This would allow each of the girls to reunite with Luffy and see what he has become.
Yonkou: I figured to get the Yonkou in the story that each of their main territories would be the location of one of the 9 keys. I would allow Luffy to battle the Yonkou since Sasuke had to struggle against the 5 kages.
BlackBeard: He would be Orochimaru's equivalent. Both Blackbeard and Orochimaru are main villains in the series, both are very strong and both power hungry and sneaky backstabbers.
Akainu: He would be Danzo's equivalent. Danzo made Itachi suffer similar to how Akainu killed Ace. Both Danzo and Akainu are very strong and cold and calculating.
Ace: Itachi's equvilent. Despite being dead and would stay that way, Luffy looked up to him a lot just like how Sasuke looked up to Itachi. Likewise just like how Itachi was looking out for Sasuke all the time before his death, Ace looked out for Luffy a lot before he died. Furthermore just like how Itachi was a driving force behind Sasuke's corruption, so too would Ace be a huge factor in Luffy's dark path.
Uranus: Would be based on The ten tailed Juubi. Not the same. I've decided to make it look like the Kraken from Clash of the Titans since both seem to have 10 tails and the Kraken is big, scarier than any Sea King and could count as an ancient weapon.
Warlords: I don't know how to incorporate them in the story. They may or may not appear. Hancock for sure though would appear.