Tanjiro is a cheerful and kind character who goes along well with others in Demon Slayer. However, his decision to keep Nezuko under his care led him to face severe backlash from the Hashira. Not only was Tanjiro protecting a demon, but he had also brought her to the Demon Slayer Corps, which was an audacious move. Although everyone was collectively hesitant about Tanjiro’s status as a demon slayer, Obanai Iguro hated him more than the others.
Obanai’s hostility towards Tanjiro explained
Obanai Iguro, the Serpent Hashira, has a generally harsh and abrasive attitude towards others. Other than being strict with Tanjiro, he hates Giyu Tomioka, the Water Hashira. Obanai has no regard for those who break rules and disrespect the code of conduct, which could be a possible reason why he is usually cold towards Tanjiro and Giyu.
Giyu, though nonchalant, is seen stepping on Obanai’s nerves by going against the Demon Slayer rules. The Water Hashira vouches for Tanjiro who wants to protect his demon sister. Moreover, Giyu makes arrangements to make room for Tanjiro and Nezuko in the Demon Slayer Corps, which further annoys Obanai.
This is where Obanai’s passionate hatred for Tanjiro begins. When Tanjiro enters the Ubuyashiki Mansion, Obanai bullies him along with Sanemi Shinazugawa, the Wind Hashira. So much so, that he shows callousness towards Tanjiro through his words and actions.
When Tengen Uzui mentions that someone Obanai hates the most survived against the Upper Moon Six demons Gyutaro and Daki, Obanai is shocked. He immediately realizes that Tengen is talking about Tanjiro. The Serpent Hashira remains in disbelief that the rookie swordsman prevailed after defeating one of the Twelve Kizuki.
Although Obanai’s dislike towards Tanjiro can be attributed to Tanjiro’s attempt at protecting Nezuko, it could also be due to Obanai’s short temper.
However, during the demon slayers’ fight against Muzan Kibutsuji, Obanai defends both Giyu and Tanjiro against the villain’s attacks. Thus, he proves that he harbors affectionate feelings towards his comrades beneath his tough exterior.