Genya Shinazugawa is a Demon Hunter of the Demon Killing Corps. He is also the younger brother of the Wind Pillar Shinazugawa Sanemi.

Early on in the series, Genya had a short build which stood slightly above Tanjirou Kamado. He had short, messy back hair that what shaved off at the sides. thin eyebrows, and a scar that is covers most of his face's width.

Later on, he reappeared with a wilder look as his height changed significantly, making him taller than most and now has longer hair reached down to his neck. He also gained a large, muscular build along with this as well as various scars all over his body.

Genya is a foul-mouthed and ill-tempered individual with a "lone wolf" character who refuses any help from others and does not show any interest in being polite or having any manners.

This changes later on when after he fought Hantengu, an Upper Moon demon, along with Tanjirou, Kanroji Mitsuri; the Love Pillar, and Nezuko Kamado, and was not as imposing as before.

(Source: Kimetsu no Yaiba Wiki, edited)