[genya]

They come out at night because they are sensitive to sunlight and it kills them; they also eat human flesh and kill themselves with sunlight or with a katana/gun.

Genya was a muscular young man of considerable height, standing at 180 cm (5'11"). His hair was black with yellow tips, shaved on the right side and reaching below his shoulders on the left. He always wore it loose. His eyes were large with small irises, and a prominent scar marked the right side of his face. This scar was inflicted by his mother, who had transformed into a Demon and tried to kill him.

He wore the standard uniform of the Demon Slayer Corps with its characteristic purple yukata.
When Genya becomes a Demon by eating demon flesh, his hair lengthens abruptly, becoming curled with small yellow spots at the tips. Likewise, the sclera of his eyes turns black and his eyes acquire a yellow color, in addition to his nails and teeth growing.
He's a boy with a bad temper, except with Muichiro; he's somewhat sociable and kind.
Family:
Kyogo Shinazugawa (Father) dead
Shizu Shinazugawa (Mother) dead
Sanemi Shinazugawa (Older Brother) alive, Wind Pillar
Shuya Shinazugawa (Younger Brother) dead
Hiroshi Shinazugawa (Younger Brother) dead
Koto Shinazugawa (Younger Brother) dead
Teiko Shinazugawa (Younger sister) dead
Sumi Shinazugawa (Younger sister) dead

Genya's past
He grew up in a home with seven siblings and an alcoholic and abusive father. After his death, Sanemi and Genya vowed to protect the rest of their family.
One night, their mother transformed into a demon and attacked her young children while Sanemi was out searching for her. Five siblings died in the attack.
Genya found Sanemi with a bloody gun in front of his dead mother's body (which was fading away in the sunlight). Not understanding that Sanemi had killed her to save him, Genya called him a "murderer," severing their relationship forever.
Years later, Genya joined the Demon Hunters solely to apologize-

Having no talent for Breathing Techniques, he began eating demon flesh to gain temporary strength and regeneration.
Sanemi constantly rejected him and pretended to hate him in order to force him to leave the hunter corps so that he could lead a normal and safe life.
Genya gets nervous and his face turns as red as a tomato whenever he's near a girl.

Sanemi is Genya's only brother, who is the Wind Pillar, and is about 21 years old. He pretends to hate his brother Genya so that he will stop being a demon slayer.

Muichiro is a short teenager, standing at 160cm tall, with fair skin. He has long, straight black hair that fades to a bluish-mint green as it approaches his waist. He usually wears it loose, with a few strands sticking out slightly on either side of his head, a slightly shorter set of hair framing his face, and a stray fringe across his forehead. He also has large, bluish-mint green eyes that often give his expressions a blank look.
His signature attire consisted of the classic uniform of the Demon Slayer Corps. The most notable customizations were: the fabric of the entire uniform was lightly dyed turquoise, his jacket and trousers were loose-fitting at the bottom, and on his feet he wore dark blue tabi socks and a pair of white zōri sandals with dark blue straps.
past:
Muichiro grew up in a humble family of lumberjacks. At the age of 10, a double tragedy left him alone with his twin brother, Yuichiro.
His mother died of bronchitis and his father died that same night after falling off a cliff while searching for medicinal herbs in the middle of a storm.
Muichiro was optimistic and wanted to help others, but Yuichiro, hardened by pain, was cold, pragmatic, and constantly belittled him to "protect" him from reality.
A year later, a demon attacked their home. Yuichiro lost his left arm trying to protect Muichiro. In a fit of blind rage, Muichiro defeated the demon using lumberjack tools and logs. Upon returning home, he found his brother praying for his salvation before he died.
Following the trauma, Muichiro was rescued by the Ubuyashiki family, but he developed dissociative amnesia.

It takes place mainly during Japan's Taisho Era. 1926.