The life of a demon slayer is one of hardship. Many who train do not make it through the basics; others die during the final selection. It takes grit, courage, and inner strength to succeed as a demon slayer, all things Zenitsu Agatsuma isn't. Yet, he is one of the most powerful slayers in this world.
As a young boy, Zenitsu had no one until he fell in love. Something that wouldn't surprise fans due to Zenitsu's womanizer tendencies. Wanting to please her, Zenitsu gave the girl a large sum of money, leaving Zenitsu in debt. With the cash in hand, she left him for another man. At first, Zenitsu believed he would have to work off his debt; Jigoro Kuwajima, the former Thunder Hashira, paid off the debt. In return, Zenitsu was to train with Jirgoro to become a demon slayer.
Related: Demon Slayer: Every Member of the Hashira, Ranked in Terms of Strength
During his time training, Zenitsu attempted to escape many times, only to be brought back by Jigoro. Zenitsu believed that he would die, either from the training or as a demon slayer. Still, Zenitsu grew in strength, even if he never noticed, and his relationship with his teacher developed as well. Zenitsu took to calling Jigoro 'gramps'. One day while hiding from his teacher, Zenitsu climbed up a tree, where he was struck by lightning. He survived the fatal strike, but his black hair was now blond.
For someone training with the former Thunder Hashira, having survived a lightning strike was undoubtedly a sign of Zenitsu's power. Regardless, Zenitsu still didn't believe he was as powerful as Jigoro claimed him to be, having only grasped the first from, thunderclap and flash. Compared to all the other Demon Slayers who have mastered all the techniques, only having one seems
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