So yeah, try this theory . I know all of youse be like " Hell No!!" but see it more as of a possibility than an ****
Luffy's heart removed by Trafalgar Law
My current belief is that Trafalgar Law is the man who will kill Luffy at the end of the series, that is, once Luffy obtains One Piece and leads armies against the World Government and wins the war.
Motives
Law is known throughout the world as the surgeon of death, Apoo here:
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Says that "Law is infamous for his cruelty." Why would a man who is known for cruelty help his rival? It says here:
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that Law wishes to be Pirate King, which confirms Luffy and Laws rivalry. One thing is for sure, unlike the other Supernova, Law is willing to let the other pirates kill one another... Law is now confirmed as a Shichibukai and sent the hearts of 100 pirates. I had presumed he was waiting for Luffy to find One Piece in order to be Pirate King himself but it seems the position he really wanted is shichibukai. However, this still doesn't change much, since Law explicitly stated that, "One Piece isn't going any where" which clearly means that Law continues to be Luffy's rival.
Luffy's heart
That dark back ground is depicted (in my mind) in a way to make us think that Law has a hidden agenda and that look on Law face definitely looks suspicious to me. Also, what is Law hiding beneath that towel:
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It could be Luffy's heart. Law says here :
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that Luffy's life is currently being preserved, which maybe hinting at removal of his heart with his (Laws) powers; preserve can also mean to prepare for future use as though for operation or something far more sinister. Several references are made to hearts metaphorically and literally: Law's pirate crew is called Heart pirates, Jinbe's heart is mentioned, Hancock who's an expert of effecting hearts is present, Luffy's heart is mentioned specifically here
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furthermore, the bottom panel on this
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Hawkins says that Luffy's survival rate never becomes zero no matter how many times he tries, which may indicate that Luffy's heart is no longer within his chest. This could be Oda's way of foreshadowing (hinting) Luffy's heart being removed. Also, after helping Luffy, why would Law be sweating/nervous from what Rayleigh says here:
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Law was smiling when he first saw Rayleigh on Sabondy Archipelago, but on that image, Rayleigh only says "Now then" nothing to get nervous about unless he had done something he shouldn't have. It's also worth a mention that Law was recalling something as he looked at Luffy's Strawhat here:
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What's Law thinking about? I believe he was recalling the events of Sabondy Archipelago and this:
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in particular. It's as if Law is trying to connect Luffy and Rayleigh via this Strawhat as well as some of the mysterious surrounding the Jolly Roger pirates. Perhaps Law accurately deduced that the hat originated from the Roger pirate crew? It's quite possible Law thoroughly examined the hat to see if something was written on it which may give him a clue to find One Piece. I mean, it's often the case that we forget that this manga is about treasure hunting, specifically the world's greatest treasure, One Piece.
How was Luffy's heart removed?
You can clearly see here:
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or here:
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that, Law can decapitate individuals without killing them; notice how the heads are talking. This is how Law could "preserve" (that's a quote from Law himself) Luffy's heart until "there's a position he needs" which I translate into meaning Pirate King.
The heart pirates, pirate flag resembles Luffy's face than anything else. For me, this is foreshadowing Luffy's death which will make Law the most famous man in the world.
Addressing possible problems with this theory
There are people who claim that, Law has a range restrictions on his devil fruit. This is perfectly logical to assume because Law has required room (technique) to create a spherical region in which can slash his opponents up. However, I have considered the possibility that once cut up Law's powers would keep you alive because on this
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Law's room is not active so therefore range may not actually be a restriction and how long a persons body is kept alive may not have a duration. Watch the anime of a head being able to talk even while Law deactivates his powers:
Another problem which needs to be considered is the fact that in normal conditions Luffy shouldn't be able to pump blood around the body without a heart, and he would notice no heart beat over the 2 years since the operation. That's a valid point to make. What we don't know is the full extent of Law's powers and how One Piece logic works in this regard. I can only infer that Law replaced Luffy's heart with a cybernetic heart; possibly taken from one of the pacifista or Luffy doesn't need a heart (in the same way White beard didn't need a side of his head) so long as the heart which Law now owns is preserved.