It looks like he has eaten a chunk out of Aizetsu while beheading him, resulting in his monstrous appearance. However, he has not actually been turned into a demon. Although he looks like one, he is still a human. Genya's unique power lets him consume demon flesh to gain their characteristics.
Genya was sliced up by Kokushibo, but the consumption of his hair allowed him to regenerate immediately. He also consumed Kokushibo's sword which was made out of his flesh. In the end, Kokushibo and Genya died without fully realizing the love their brothers had for them.
Why does Genya eat demons? He consumes demon flesh because it allows him to temporarily gain that demon's abilities despite being a human. This is a power that is unique only to him. In the latest episode of Demon Slayer, fans could watch him recite the Amida Sutra.
Sometimes, presumably because of how concentrated a demon's blood is, Genya can gain attributes related to the demon he devours, like when he gained Kokushibo's eyes, hair, and Demon Slayer Mark, with his shotgun even gaining the appearance of the Upper Rank's katana.
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.
Demon Consumption & Empowerment: Genya possesses unnaturally strong jaws and special digestive organs which allow him to tear off and consume the flesh of demons without any adverse effects. By devouring demon flesh, Genya gains demonic characteristics, such as fangs, dark sclera, and unique yellow tips in his hair.
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.
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 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.
Genya remains loyal to the Darkling, but his nichevo'ya mutilate her when she betrays him to help Alina escape in Siege and Storm. She joins Alina and helps in taking the King down. She marries David Kostyk and becomes a member of the Grisha Triumvirate.
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.
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.
Demon Slayer: Kimetsu No Yaiba, Volume 20 continues as the Demon Slayer Corps' initial confrontation with the most powerful of Muzan's demons, Kokushibo, has left Tokito severely wounded and Genya cut in half.
No one killed Sanemi Shinazugawa. Sanemi almost died when he tackled his sister Genya from a window in order to protect her from a demon attack, but was saved by his friend Masachika who healed his wounds.
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.
Genya is always angry at others because of everything he has gone through in his early life. Every waking moment is an attempt to become stronger, even if it is at the expense of his life. He is doing this only for his brother to acknowledge him.
Genya Shinazugawa's reincarnation and his brother Sanemi's reincarnation/descendant, Sanehiro, are policemen.
Genya's weapon in Demon Slayer
However, that takes away his ability to use breathing techniques, which is why Genya is unable to master swordsmanship. Nonetheless, Genya's weapon, Nichirin Shotgun has abilities similar to that of a demon slayer's sword that allows him to kill demons without a blade.
Genya has some minor infatuation on Sakura Igarashi. He was very extremely jealous of Hikaru Ushijima for having his crush and later he might become suspicious about his business that Hikaru mentioned.
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):
Sanemi and Giyuu are married and live in hollowed out tree near a bunch of glowy mushrooms. Sanemi works at a construction site while Giyuu is a humble fisher.
However, Giyu Tomioka does not marry anyone in Demon Slayer manga. While romantic subplots do exist in the series, Giyu's character arc focuses primarily on his growth as a warrior and his relationships with fellow demon slayers.
Despite this crude and reckless battle style he managed to survive and kill several demons, later upon looking back at his past exploits Sanemi admitted that the only reason why he survived was due to sheer luck and the unique aroma of his blood that caused the demons to become intoxicated, drunk and less focused in ...