why did akaza kill himself

Akaza killed himself because he lost the will to keep fighting and accepted defeat after realizing the true meaning behind his long quest for strength. Throughout his life and as a demon, Akaza was driven by a desire to protect his wife Koyuki and to be acknowledged for his strength. However, during his battle with Tanjiro and Giyu, memories of his past life as a human and the love he once had flooded back, making him question his existence as a demon. Akaza was not like other demons who fought desperately to survive; he respected strength and hated weakness. When he realized that fighting no longer gave him purpose and that he was only causing pain, especially betraying the memory of his wife, he chose to end his own life rather than be defeated by opponents he considered weaker. He consciously stopped regenerating his body, which in the world of demons was effectively a form of suicide because demons typically survive any physical damage. His death was an act of reclaiming control over his fate and symbolized a form of redemption and release from the curse of immortality that Muzan had imposed on him. Akaza did not simply lose the fight; he chose to let go as a way to honor his past and to escape from a meaningless existence as a demon weapon of Muzan.