One Piece: Shadow monarch? I'm Just Logistics!

'I'm not an ambitious person,' is something Reiner often says. He just wants to hang around with the Straw Hat crew, traveling the world while collecting the souls of the dead. From Kuro... Arlong, then to 'Old Sand' (Crocodile)... the Golden Lion (Shiki)... As he gathered more and more, the 'style' started getting progressively weirder. A demon with goat horns and a snake tail? Okay, maybe I can understand that. But a 'Chainsaw Demon'? What the heck is that? And where did you even pull this 'Sukuna' from?! When the Summit War kicks off, Sengoku and the Three Admirals stare at Reiner, who is sitting calmly upon the execution platform. 'What? You're saying these incredibly strong individuals are undead beings controlled by him?!' 'How is that possible! Isn't he just some handyman doing chores for the Straw Hat crew?' 'Seriously, man... You call *this* logistics?!' Hearing this, Reiner gets annoyed: 'If doing literally every kind of job isn't called logistics, then what is!?' ------ (Story follows the Straw Hats' journey + original plot elements. The main character is neither overly righteous/naive nor does he turn evil/dark.)