Genya is so driven to become a Hashira because of his older brother Sanemi, who went on the become the Wind Hashira. He isn't driven by a sense of rivalry though, he wants to earn the respect of his brother in a twisted and tragic way.
For a short amount of time, he can become a demon using his bite strength and his special digestive organs." Basically, as a result of his serious gnashers and iron stomach, Genya can devour demon flesh and gain characteristics like the sharpened fangs, frosted tips, and black pupils seen in the most recent episodes.
According to the official Kimetsu No Yaiba data book, Gyomei took in young Genya as a "stepson" and became his father figure. He wanted to train him and make Genya his Tsuguko, but couldn't because of Genya's unique inability to use Breaths. That's why Gyomei trains him in other techniques instead to help compensate.
In the simplest terms, the reason that Genya can't use Breathing Styles stems from his inability to achieve the total concentration breathing that other demon slayers use in order to access their abilities.
Unknowing that his mother was the demon, or "wolf", Genya screamed at Sanemi and labelled him as mother's murderer, an action that he reminisces regretfully.
Genya Shinazugawa is the student of Tokyo High School and Sakura Igarashi's crush. He is also the Sanemi Shinazugawa's younger brother. He later snatches Demons Driver from Hikaru so, Genya can temporarily become Kamen Rider Over Demons to stop the chaos by Fenix & Demon Slayer Corps.
Genya was killed by the Upper Moon 1, Kokushibo, but not before helping the others take him down. As he was dying, his brother Sanemi regretted how strained their relationship have become, and wept as he begged the heavens to spare Genya. Like a demon, his body disintegrated as he died.
For a short amount of time, he can become a demon using his bite strength and his special digestive organs." Basically, as a result of his serious gnashers and iron stomach, Genya can devour demon flesh and gain characteristics like the sharpened fangs, frosted tips, and black pupils seen in the most recent episodes.
When he found out he had no talent as a swordsman, he felt mentally exhausted. His mental state pushed him into a corner. where he ended up eating a demon. Then he discovered this idiosyncrasy as his own ability.
Genya possesses an astonishingly powerful set of jaws and teeth, enabling him to effortlessly tear through the flesh of Demons and consume them without any negative repercussions on his own body. This extraordinary ability also provides a glimpse into the remarkable efficiency of his digestive system.
Genya is moved to tears and apologized after hearing Sanemi's reasoning behind his rudeness. After their battle with Kokushibou, Genya apologized again for blaming Sanemi and thanked his brother for protecting him before succumbing to his wounds and crumbling into dust, leaving Sanemi stricken with grief.
The only person who put his life on the line to save Genya was blamed and called a murderer. Such a backstory has surely traumatized the sibling duo. Genya is always angry at others because of everything he has gone through in his early life.
Sanemi managed to survive the battle against Muzan, if just barely. Unconscious and straddling the edge of death, Sanemi chose not to go to Heaven with his siblings, but to lovingly join his mother in Hell because she'd killed most of her children after she became a demon.
Demon Slayer season 3 episode six did more than just give us some great action, it also showed us Genya's backstory. Similar to Tanjiro, Genya's family was torn apart by tragedy. His life was destroyed after his mother was turned into a demon and had to be killed by his older brother Sanemi.
Genya is the first of all Grisha to share her specific talent, and she is curious, knowledgeable, and kind. But she is also tool used by the Darkling to endear himself to the royal family by gifting her talents to the queen (and making her body easily accessible to the king, who sexually assaults her).
Siege and Storm
Alina urges Genya to come with them but Genya cannot and is left behind. Towards the end of the book when the Darkling finds Alina, we find out that the Darkling unleashed nichevo'ya on Genya because she spared Alina. Her skin is scarred all over and she only has one eye left.
Alexander III wants Genya to be beheaded for high treason and murder, while it becomes clear that he raped her. Genya confesses that she poisoned her own skin so that the king would consume it when he kissed and touched her.
Genya's tragic past
Genya's flashback explains how they had an abusive father, who used to hit his children and wife frequently. After their father died, the two brothers stay close, and the responsibility of looking after their family falls on Genya and Sanemi.
More importantly, Genya is able to become stronger after consuming a demon. For the most part, Genya gets an enhanced physical constitution (which makes up for his inability to use Breathing Styles) along with potent regeneration.
Kyogo Shinazugawa (不死川 恭梧, Shinazugawa Kyōgo) is a minor antagonist in Demon Slayer: Kimetsu no Yaiba, but an important character to Sanemi Shinazugawa and Genya Shinazugawa, being their abusive father who is partially responsible for the wrathful personalities the two siblings have.
So, Genya originally wore white, the color of the servant uniforms, because she was seen as a servant by the queen. But later in the story, she is allowed to wear Grisha colors, and Alina describes her kefta like this in Shadow and Bone (Chapter 20):
The Wind Hashira has one of the saddest backstories in Demon Slayer. His mother had turned into a demon and had killed five of his siblings. He was forced to kill his own mother in an attempt to save his only remaining brother, Genya.
Sanemi not only witnessed his five siblings slaughtered by his mother but also killed the latter so that she could not hurt Genya. This took a heavy toll on Sanemi and turned him into a cold-hearted person with immense hatred for demons. This is why he enjoyed torturing Nezuko by stabbing her with his sword.
Shinobu Kocho is a capable Demon Slayer whose worthy of being the Insect Hashira. That being said, she's arguably the weakest Hashira when it comes to pure strength.