Inosuke Hashibira is one of Demon Slayer's biggest enigmas. Little is known about this character's life, other than the little hints the anime has dropped along the way. He is a character that is hard to miss; mispronuncing everyone's names, gobbling his food with no care for dinner etiquette, and his aggressive nature are all signature traits of Inosuke.
Inosuke's signature staple, however, is the boar's head that he wears on top of his own. In a series full of eccentric characters, Inosuke's unique appearance really stands out. So what's the deal with this stylistic choice?
Inosuke's Childhood
Inosuke's was born into an abusive home, more specifically, an abusive father. When he was an infant, his mother Kotoha took him and fled their home. After escaping, the two were taken in by Doma, the leader of the Paradise Faith cult. Unbeknownst to them, Doma was a member of the Twelve Kizuki, namely Upper Rank Two. Kotoha learnt that Doma was eating his followers, and fled once again with baby Inosuke, with Doma in pursuit. Atop a mountain with nowhere else to run, Kotoha dropped Inosuke into the river below and was in turn consumed by Doma. Inosuke was then discovered and raised by a wild boar.
His introduction to the life of a demon slayer began when he ran into one on his mountain right before the Final Selection. Inosuke proposed a contest with the demon slayer, declaring that if he was victorious, he would take his swords. He won the competition, learnt about demons and decided to participate in the Final Selection. Subsequently, he survived and became a new member of the Demon Slayer Corps.
First Impressions
When Tanjiro and Zenitsu travel to the Tsuzumi Mansion to rescue some children from the demon Kyogai, his blood demon art changes the direction and placing of the rooms and corridors in the mansion. The pair discover Inosuke clad in his boar head towards the tail-end of these events, who ended up trapped in the mansion due to the confusion of Kyogai's blood demon art.
After the three of them escape with the children, Inosuke tries to kill Nezuko, not knowing that she is Tanjiro's sister. In true Inosuke fashion, he picks a few fights with Tanjiro and Zenitsu, boasts his athletic prowess, and misremembers everyone's name.
Why The Boar's Head?
Given that Inosuke was an infant, he could not remember his birth mother. To him, his mother was the sow that raised him. She eventually passed away, so it is possible that Inosuke wears a boar's head as a remembrance of her. This would explain why he almost never removes it, the head is familiarity and comfort. The boars are his family, and don't people normally resemble their families?
Since Inosuke was raised by wild animals, it would be no surprise that he adopted their way of life. In nature, some animals execute various means to ward off others animals that may harm them. In Inosuke's case, he may be wearing the boar's head to be as frightening as possible to protect himself from any impending danger. His wild personality and fighting style also compliment the wild animal sitting on Inosuke's shoulders.
A running joke in Demon Slayer is Inosuke's surprising beautiful face. It is comical that someone as uncouth as Inosuke has the most dainty facial features of all the characters. His precious face has been the butt of many comments and events throughout the anime, which infuriates Inosuke. It can be argued that perhaps covering up his delicate face with something as terrifying as a boar's head, he will avoid comments about his face. Alternatively, it is possible that Inosuke perhaps wants to completely hide his human face from the world. After all, if his mother is a boar, surely he is one too.