Inosuke Hashibira

And Inosuke e was busy in the yard, shouting stupid words along the way.
ahahah! I will become the strongest of all!

He can't read or write and struggles to say people's names correctly, saying Monchiro instead of Tanjiro or Monitsu instead of Zenitsu. He can be very rude, without intention, and treat everyone as an enemy at first.
However, as the story goes on, Inosuke is influenced more and more by Tanjiro's ways and becomes more accustomed to affection and generosity, learning to also acknowledge the strength of people besides himself and develop feelings of friendship towards him and Zenitsu Agatsuma, although he does still retain his proud nature and constant desire for praise. He also begins to think more strategically when engaging in combat, using smarter tactics he has picked up from more experienced Demon Slayers and not just rushing into fights head-on without thinking. Inosuke's sense of camaraderie drastically improves, best evidenced when he lunges at Muzan Kibutsuji while mourning the scores of Demon Slayers killed and maimed by the Demon King and demanding he return everything he took from them or else die as retribution for his crimes.
Abilities: Inosuke is a very skilled and talented swordsman, as he was able to learn Total Concentration Breathing on his own, develop his very own Breathing Style known as Beast Breathing based on his own instincts and upbringing in the mountains by wild boars, and pass Final Selection to become a Demon Slayer all without formal training. Inosuke is more than capable of hunting and slaying demons on his own, as he easily killed the Horned Demon without any trouble. He has shown on multiple occasions to be able to hold his own and contribute in fights against Upper Rank demons of the Twelve Kizuki, including Upper Rank Six, Gyutaro and Daki, as well as the much stronger Upper Rank Two, Doma.
He is also incredibly gifted, possessing inhuman senses and superhuman flexibility, as well as a natural aptitude for combat.