Yomi Yomi no Mi

The Yomi Yomi no Mi, is a Paramecia type Devil Fruit, which allows the user to come back to life after being kllled. Initially, this Devil Fruit has no effect except for the usual side-effects such as not being able to swim. When the user dies, however, it brings them back to life once. Upon death the spirit is haulted from traveling to the realms of the dead and is instead allowed to locate its body and be revived. However, this does not prevent the users body from decaying, hence Brook's skeleton appearance. The term, "yomi", could have one of two meanings, and both are implied in Brook's explanation of the fruit. It could be short for "yomigaeru" (蘇る, "revive" or "reborn"), or it could come from "yomi no kuni" (黄泉の国, "realm of the dead" or "the underworld"). It was eaten by Brook.

Strengths and Weaknesses
The major, if not only, strength of the fruit, as demonstrated by Brook, is that it just gives it's user a second life after being killed. 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 power 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. Furthermore, while the Fruit allows the user's spirit to once again return from the afterlife, it does not allow it to automatically return to the physical body that it once resided upon during its mortal life. Thus, it is then up for the disembodied soul to search for the corporeal body in order to once again reunite with it. Though the user gains a second life, their body however will continue being a lifeless corpse and will continue rotting away until the user's soul can find back the body. When the user's soul finds back their body, the powers of the Devil Fruit will fortunately support the user's well being in the case that their body maybe 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. Other than that, the user is affected also by standard Devil Fruit weaknesses.

Usage
While the fruit's only major fruit's bestowed power is only usable after death, it's 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 been decomposed long ago. He is able to move and stand up without the presence of tissue and muscles to support him, as well as being capable of getting tired or worn down despite not having any of those factors to begin with. 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 broken in battle. Depending on the situation, Brook is also able to produce organic matter such as poop, tears, and even blood from his nose despite not having any organs nor bodily liquids to produce such matter.

Due the fruit's powers holding up and moving his light skeletal frame, Brook is given an extremely light body. Brook is able to perform some things due to this advantage such as jumping up very 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 isn't 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 too long. He can maintain this messiah-like feat for the first few moments upon touching the water but eventually he would sink down below like any normal pile of bones if he stays too long running on water due to exhaustion.

Being a skeleton animated by the fruit's powers also allows Brook to do things that most other people can't 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 a electrically charged projectile. Due to the lack of organs, Brook is also able withstand some deadly attacks to a certain degree. He is for instance, able to withstand his skull being shattered to a certain degree and also able to withstand having several of his ribs broken. Also due to the Devil Fruit powers also 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 many things because of his Devil Fruit supported form, he however can still feel pain, as well as fatigue.

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.