Kagura

Personality 

Kagura has put an act of himself as sort of a show-offish and sort of lazy person. But in reality, He is a rather calm, collected, and even tactical thinker, despite having a chronic half-resting bitch face, frequently engaging in comical behavior, and retaining his calm mind even while making threats. He has a very strong sense of justice, and a silver tongue to boot. When asked by other marines, even the most notable marines revealed they have great respect for the Vice Admiral. He takes great pride in his form of Absolute Justice, which before was trying to solve things by talking about them and trying to find more peaceful ways to resolve old grudges. But as he saw the horrors of the war of Marine Ford, He turned much more serious and oddly calmer now. He honestly lost many good friends because of the war, so he accepts the new fleet admiral's views of Absolute Justice. But Still believes in the belief that The innocent shouldn't be caught up in the affairs of marines or pirates or as he refers to them, the sinners of the sea. He even accepts to use his devil fruit as a way to punish other marines who disobey his or other higher-ups' orders. Overall, He becomes much more ruthless and cutthroat during and after the events of the war. Stating he lost his true sight, before that.

But a chance meeting with Koby and Monkey D. Garp, during the transferring of the marines. They were surprised at how cold Kagura had grown to the world, thanks to the war, and Sakazuki putting more and more pressure on him to help fight again. They decided to help him claim back some of his old views again. Koby asked Kagura if they could talk for a bit about Kagura's life. Garp decided to join them, and as they talked- Kagura finally broke down from the stress of it all, saying he honestly was lying about wanting to see things of the new Fleet admiral's way after all. But rather was under so much mourning and sadness he lost himself to the world. Koby and Garp assured him, that he was okay for feeling like this, and Koby told him about his time training under Garp, and how He was told by other marines about the a very well respected marine that was always called the 'Kind Quartz'. This shook Kagura to his core and reminded him of who he should be, not what he should be, thus a much kinder version of himself can be seen after the time skip. 

Sekiei Sekiei no Mi (Toei Translation: Quartz-Quartz Fruit)

This Logia Devil Fruit allows the user to create, control, and transform into Quartz Crystal, thus making the user a Crystal Human ( Kesshō NIngen ). The user can access near-infinite amounts of Quartz/The Abilities of Quartz. Quartz is a type of natural element that can be classed as a Logia. But also it could be considered as a Special Paramecia, mainly because quartz can be manmade in labs, but considering this factor- Both Paramecia and Logia versions of this devil fruit are possible. Now moving on, as seen all Logia devil fruits have a natural state of matter, Quartz is a solid state of matter, allowing for much more defense skills for this devil fruit. If we looked at the Mohs hardness scale. Now This scale is based on how much it takes to scratch precious to semi-precious crystals/stones. Quartz is scaled at 7,  which on the hardness scale is only 3 points from the diamond itself. But we can improve this hardness with Armament Haki or Conqueror's Haki, which can make the hardness over 10+. Thus truly making this one of the most defensive logia. But Haki in general is a double-edged sword for this Logia. In contrast, Haki can greatly enhance its natural hardness when a more advanced user of either Armament Haki or Conquror's Haki, can easily break into the quarts with blunt force mainly. But again this is mainly a major problem for all logia.

Now we move to the unique properties of Quartz itself. While it has an extremely good ranking on the Mohs Hardness Scale, it does have a major strength it's superior in strength of Defense. What truly amazes others is Quartz's melting point, which is extremely high at 1,650 C ( 3,002 F ). Keep note of this when the other logia types come into play. Also seen from the central bio that its blunt nature of being crystal. This means that Kagura mainly uses the quartz that comes off him for blunt-force trauma attacks to stunt other targets. But this doesn't mean Kagura hasn't figured out tricks to do actual wounds with Quartz, he can pinch off shards of himself, and fire them off at hyper-sonic speeds to stab through someone with ease. Quartz is also a great conductor when exposed to mechanical stress to generate electric charges, thanks to Kagura and his true mentor, Dr. Vegapunk. Have invented a special set of copper and brass knuckles he uses. it is also noted, that Kagura has figured out how to trap others in his quartz too. 

Now we get to the strange weakness of this devil fruit, Hydrofluoric acid. This type of Acid Is a highly corrosive chemical that effectively dissolves quartz, glass, and other silicates. But this acid is extremely hard to come back and also very hard to handle. it is also stated by Kagura, that his quartz body can be brittle at times, which can cause fractures in his body to cause him a sort of numbing feeling in that area. Also for him to regenerate outside of battle, he must eat vast about of food with high amounts of silica in it. Also noted is a form of recovering his mass from overusing his devil fruit, which is silica acid. Overall, This devil fruit is extremely defensive even compared to other major types of logia.

 Donquixote Doflamingo was able to trick and use this type of acid to greatly hinder Kagura and force him to retreat to regenerate in a tank-like Bathtub-filled liquid that had high amounts of other silicates in it. He was hindered to the point, he was forced to stay in a Bathtub of liquid during the whole Dessrosa arc.

Backstory

The Origins of the Beifong Families go back for generations, Each Beifong Family would have their own 'Title' to their mixed names, The 'pure' Beifongs, were talented Tea Masters, who were gifted for their talents and were allowed to stay with many royals families as their personal tea masters and then chefs too. The Li Beifong Family was known for their amazing skills with Fireworks and tricks with show-stopping forces. The Cheng Beifong Family was known for their amazing craftsmanship skills, and the Chan Beifong Family was as well. But there was one forgotten Branch of all the Beifong Families, who were thought to be worthless for not having any truly unique skills. The La Beifong Family, they were always had to survive on scraps of life at times and were thought to have disappeared... Until a Young Man was born in a very poor area in the grand line, Known as Shiwen La Beifong. The thought to be the truly last member of the La Beifong family. Because his father and mother had to keep him safe, they ended up dying trying to get him food all the time. Solely because they wished for him to live, to survive, they ended up giving him the Sekiei Sekiei no Mi. Which he ate out of pure hunger as well.

During his years of youth, it was shown he was a gifted mind. He could figure out various things with ease, so he made a life of fixing and repairing things for Berri. Until he was found by MADS, and taken in under the wings of them, only at a young age too. During his years of working with the likes of Dr. Vegapunk, Judge Vinsmoke, The MADS Scientist that be later known as Queen The Plague, and Caesar Clown. When MADS was forced to dissolve, Young Shiwen had to make a deep choice within his own life, stay with Vegapunk and Caesar, who had shown him quite a bright future, Go with Judge and focus more on the aspects of cloning that both at mastered thanks to Shiwen's Prototype Cloning Chambers, or Go with Queen to learn about how to generate viruses, etc. Shiwen's choice was clear, He decided to stay with Dr. Vegapunk, and Caesar Clown, and Join the Marines... Over time, the Marines managed to recruit Shiwen, who at this time, had tossed his old name Shiwen La Beifong, for a shorter and easily known name he wanted 'Kagura'. into their ranks, which he quickly adapted to, thanks to his devil fruit, which he had been learning to master over time. He was then taken under a younger Sakazuki who trained him intensely to understand how Haki works, he made sure to get Kagura strong enough to see his ideals of Absolute Justice. 

Kagura was forced everything to train non-stop to master Armament-type Haki, then studied a bit of Observation-type Haki, But in the special case of Kagura, he was born with Conqueror's Haki. But during his time as a marine, he was always allowed to work in a special lab with Vegapunk where he could help develop weapons and technology when he could. But by canon timeline, Kagura had been given the code name of Shirohebi. He was in charge of a special project that had been kept under wraps from the SSG, and even Vegapunk himself for nearly 16 years. During the events of the Marineford War, The 'Project' was able to escape. This greatly distressed Kagura and added to the factor of losing Multiple of his close friends in the mourning, he vowed to take out any pirates who came his way after that. But a Chance Meeting during the two-year time skip greatly shakes Kagura back to his senses, and he vows to return to his original ways and try much more peaceful ways of solving things like he originally had before.

( An Example of Kagura's Powers of the Quartz-Quartz Fruit - Done by Sketch-ice )