Yomi Yomi no Mi

The Yomi Yomi no Mi is a Paramecia-type Devil Fruit which enhances the user's soul to the point where they resurrect after their first death, allowing them to live a second time and to use several other soul-based abilities, making the user a Reviving Human (Fukkatsu Ningen). It was eaten by Brook.

Strengths and Weaknesses
The major strength of the fruit, as demonstrated by Brook, is that it gives its user another chance at life after dying once before. After death, the user continues to exist in whatever state they were revived as and can even go as far as to grant a form of "immortality" that lasts until the user suffers a second death. However, since the main attribute of the fruit is resurrection, the Yomi Yomi no Mi's power will remain dormant until the time when the consumer suffers his or her first death. As a result, until such time, the only aspects the fruit bestows upon its eater are the typical Devil Fruit weaknesses.

While the Fruit allows the user's soul to once again return from the afterlife, it does not automatically return them to the physical body that it once resided in during its mortal life. Thus, it is then up to the disembodied soul to search for the corporeal body in order to once again reunite with it. Though the user gains another life, their body however will continue being a lifeless corpse and will continue rotting away until the user's soul can find its way back to the body. When the user's soul returns to their body, the powers of the Devil Fruit will fortunately support the user's well being in the case that their body may be in a condition unable to support life.

While the fruit can make the user an undead being of sorts, it however grants the user the ability to still feel pain as proof that they have been truly resurrected back to life, regardless of what physical condition they've been revived in. This is noteworthy because it separates the power of the Yomi Yomi no Mi from the zombies created by the Kage Kage no Mi because though both powers work to make the dead come "alive" again, the Kage Kage no Mi zombies do not feel pain because they are not truly "alive" at all. However, the susceptibility to sensation seems to be selective, since Brook was able to traverse Punk Hazard's frozen terrain without any signs of discomfort, while the rest of the Straw Hats were shivering in comparison. It may possibly be that Brook is immune to damage that is based on impacting one's tissue, as Brook carried a petrified Kin'emon out of the new H2S compound without much incident, or before, when one of Smiley's blobs hissed gas on his face, he wasn't affected (he acted as his eyes were itching until he remembered he didn't have eyeballs anymore). Other than that, the user is still affected by the standard Devil Fruit weaknesses.

Brook demonstrated a new power of his Devil Fruit on Fish-Man Island after the timeskip. Brook's soul that came back to inhabit his skeleton is still able to leave the body, usually by exiting his mouth, similar to astral projection, and move it everywhere he wants to. It can even pass through walls, similar to Perona's own astral projection power. In the anime it was shown as Brook saying the word "bone" multiple times like a mantra of some sort and then his spectral form leaves through his mouth, leaving his body seemingly colorless.

When Brook is in spectral form, it mostly resembles his skeletal face (complete with the omega letter-shaped crack across his forehead) and is engulfed in spiritual flames; it appears to be not only visible but also audible to both people and animals, since Zoro and Usopp were seen being able to converse with Brook while in this form, and Pappag was shown scampering away from Brook in this state, mistaking the skeleton's soul as a ghost, therefore frightening the starfish. It is currently unknown as to how far the extent can Brook maintain this separation of his soul from his body, or if there are any limits about it at all (i.e. like when Perona uses her own spectral form, she leaves her corporeal body dormant). He discovered this power while praying during the timeskip and he used it to peek on women. This ability has also been proven useful for scouting. However, the main weakness to this ability is that while Brook has his soul out of his body, he cannot use or move his physical body and has to have someone guard him so that Brook won't be harmed.

During his fight with Zeo, Brook reveals that in the past two years he has come to know the true power of his Devil Fruit. The soul of a human that died is supposed to go to the land of the dead and stay there, but for his soul to exist in the human world it emits a powerful energy. Therefore, the power that allows him to live in the human world is neither organs or muscles, but rather his soul.

As long as his bones are not hurt, any attacks will not go to his core like when Zeo beheaded Brook, his soul managed to repair it and connect his bones together again. He has also displayed that he can transfer this energy to an object like his cane sword in which he summons the chills of the underworld, to freeze his opponent. Lastly, he has stated that he can feel the souls of others and, when mixed with his music, is able to move them.

This fruit also gives the user certain advantages over the user of the Soru Soru no Mi; Brook is capable of using the raw energy and presence of his own powerful soul to overwhelm the homies due to them being created from small pieces of souls that do not belong to them. The effects of this are visually similar to Haoshoku Haki; it renders the homies unconscious and immobile. This advantage is decreased against homies made from Big Mom's own soul, as Brook cannot overwhelm them, but he is capable of injuring them as well as even homies like Zeus and Prometheus that are made of material that cannot normally be damaged.

Usage
While the fruit's only major bestowed power is only usable after death, its secondary powers however are rather useful in keeping Brook basically "alive". Through the fruit's powers, Brook is able to function without the presence of necessary and vital body parts that have decomposed long ago. He is able to interact with the environment around him without the presence of eye balls or any other sensory organ to aid him. He, in particular, retains his ability of speech despite his vocal chords and even his windpipe have long since rotted away. He is able to taste and digest food like any other normal living thing to sustain himself. Drinking milk in particular heals him as the calcium intake repairs any of Brook's bones that may have been broken in battle. Depending on the situation, Brook is also able to produce organic matter such as tears, fecal matter, and even blood from his nose despite not having any organs nor bodily liquids to produce such matter.

Brook is able to move and stand up without the presence of tissue and muscles to support him, as well as be capable of getting tired or worn down despite not having any of those factors to begin with. Due to the fruit's powers holding up and moving his light skeletal frame, Brook is given an extremely light body. He is able to perform seemingly superhuman feats such as jumping extremely high and running on water. These allow him to travel great distances and aid him in battle. However while his light body lets him be lighter than an average person, Brook is not immune from sinking. Brook will still sink like any other Devil Fruit user when placed in water. In fact, while Brook can run on water, he cannot stay above it too long.

Being a skeleton animated by the fruit's powers also allows Brook to do things that most other people cannot do due to their need of tangible living tissue. Not only is he able to use his light weight to execute fast attacks, but his lack of flesh also allows him to execute attacks that would otherwise be harmful, such as shocking himself with electricity and becoming an electrically charged projectile. Having no flesh and organs give Brook a great advantage against carnivores, even though it will still make him angry, such as a dragon at Punk Hazard, the dragon was chasing Brook, but since he was only bones, the dragon ignored him and Brook got really mad. On the contrary, canine minks who love to gnaw on bones tend to chase after him due to his physiology. Due to the lack of organs, Brook is also able withstand some deadly attacks to a certain degree. For instance, he was able to withstand his skull being shattered to a certain degree and was also able to withstand having several of his ribs broken.

Also, due to the Devil Fruit powers allowing it, Brook also has the ability to store objects in his skull by opening it along its crack. While Brook is able to do these things because of his Devil Fruit supported form, he however can still feel pain, as well as fatigue. However, the fact that he lacks the actual organs means that Brook can fore-go most of the necessities required by humans (i.e. eating, breathing, etc.), having stayed up on his old ship for a long time with nothing to sustain himself with. Based on his own statements and comments from others, despite the lack of any muscles it appears that he is able to grow stronger through normal training. Though Brook is able to repair broken bones, he believes that all growth functions have stopped. For this reason Brook puts a lot of effort into protecting his afro, since he would be unable to grow it again if it were cut.[3] However, Brook's belief was incorrect, as he grew 11 cm during the two years he was separated from the crew.

After developing the ability to remove his soul from his body, Brook uses the intangibility to his advantage to peek at women, as well as escape imprisonment of any kind while contacting other people for assistance and scouting out things.

After two years of training, Brook has mastered the use of this Devil Fruit to the extent of knowing its true nature. He reveals that in order for his soul to remain here in this world, it produces a unique and powerful energy that is almost physical in form. He has also mastered the energy his soul emits to the extent that he can reattach his bones by using this energy such as when he is beheaded he then attaches his head back with the help of it. Brook can engulf objects such as his sword with this energy and thereby summon the "Chill of the Underworld".

Trivia

 * Brook's soul, upon returning to the mortal realm to search for his body, resembles a hitodama, a representation of the recently deceased commonly found in Japanese folklore and pop culture.
 * So far, this is the only known Devil Fruit that requires some sort of condition to fully "activate"; in this case, the user must die to trigger the effect.
 * As of now, Brook is the only Straw Hat Devil Fruit user who does not have any named Devil Fruit attacks. However, Brook does have several named swordsmanship techniques that involve the usage of the fruit's abilities.