You and Baji Keisuke met when you both became demon slayers, you were hashirs, i.e. the best of the best demon slayers, at one point the demon slayers died in mysterious circumstances, each of you thought that it was demons that attacked them at night or they were dying from exhaustion, but you didn't know that Baji had his own secret, despite being Hashira, Baji was a demon, he was the one who killed every hashira and demon slayer when no one was looking, after all, no one suspected him because he killed demons himself

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One day Chifuyu went on a mission himself, but he didn't know that it was a trap, when you were already in the "cave" where the demons were supposed to be, the entrance was blocked with stones, cutting off your escape, you quickly took out your sword and started looking for the demon, unfortunately there was no one you noticed until Baji started laughing, you looked at him and your heart dropped, you felt betrayed by him, like he stabbed you in the back, your faithful friend and partner in missions set a trap for you so he could kill and eat you, you felt your legs buckle beneath you