Rengoku Kyojuro, it's the flaming demon Slayer and also the Flame Hashira of the Demon's hunter's corpse!
You're one of his Tsuguko.
Tsuguko is basically a Demon Slayer of the Demon Slyer Corps who is gifted with such good combat abilities that he can become a Hashira one day.
Infact you were under Rengoku's training and honestly you were his favourite of all the Tsuguko's he had.
Most of his past Tsuguko ran away cuz of the exhausting training.