Demon Slayer: Kimetsu no Yaiba has taken fans by storm with its intense action and emotional storytelling. Among many beloved characters from the series, we have the tritagonist, Zenitsu Agatsuma, who stands out due to his cowardly personality that heavily contrasts with his overwhelming strength when pushed to his limits.
Zenitsu is one of the three main characters, alongside Tanjiro Kamado and Inosuke Hashibira. Despite appearing as weak-willed and always scared, he decided to join the Demon Slayer Corps. During his initial introduction, he was often seen begging for safety, crying, or trying to escape missions. However, beneath his fears lies an incredibly skilled swordsman who resurfaces when Zenitsu is asleep or unconscious.
His powers stem from his mastery of the Thunder Breathing (Kaminari no Kokyū). This style was inspired by the original Sun Breathing technique. In Demon Slayer, it is shown that the Thunder Breathing technique mimics the speed of lightning. Its movements are rapid, intense, and precise. But unlike other users who use this technique, Zenitsu has mastered only the First Form: Thunderclap and Flash (Ichi no Kata: Hekireki Issen).

However, his dedication to mastering this one form has elevated his level to become a master in this form that no one else can surpass. Other than that, he also has a unique ability to become exponentially powerful when he loses consciousness. His instincts are unbeatable, and his unconscious body relies on this skill to fight. Additionally, in this state, Zenitsu is incredibly precise, fast, and lethal.
Also in the universe of Demon Slayer, Zenitsu is considered to be one of the fastest characters. His breathing technique is focused entirely on the fast movement. This allows him to close the distance on his opponents in the blink of an eye and land critical blows before the said opponent even has an opportunity to react.
He also has a heightened sense of hearing, as it is seen in Demon Slayer, in that he can pick up even the faintest of sounds. This skill is cultivated to such an extent with him that he can hear things, including the inner feelings and emotional "sound" of people and demons. This ability is also great for pinpointing any upcoming danger and locating the precise location of the enemy.
While Zenitsu is not physically strong like Tanjiro or Inosuke, he is remarkably durable. During the whole of the series, he survives poison, burns, and high-impact fights. Furthermore, his willpower is another reason that makes him want to survive and protect others.
If we compare him with other Demon Slayer characters, Zenitsu is one of the strongest characters who is not a Hashira. It is evident at the end of the series that he managed to fight and survive one of the upper-ranked demons. Another thing about Zenitsu is that his speed gives him an edge over other experienced characters. His Godspeed and Flaming Thunder God techniques make him unpredictable and deadly.
It would make sense to claim that Zenitsu’s speed-focused combat is equal to or greater than some Hashira-level techniques in the right context. Also, he is one of the handful who have invented a technique called Seventh Form: Honoikazuchi no Kami. The translation of this is Flaming Thunder God.
This was possible because he mastered the first form of the thunder breathing technique to such an extent that he transcended it. The technique itself is a testament to his growth. It’s fast, powerful, emotional, and iconic. It’s not just a move, but rather it is the moment Zenitsu becomes who he was always meant to be.
Zenitsu’s Role in Demon Slayer: Infinity Castle Arc

During the Infinity Castle Arc, Zenitsu has a turning point in his life. It is the first time that Zenitsu fights while being fully conscious. This was the most important fight of his life because his opponent was none other than his former fellow student, who shared the same mentor and was now an Upper Moon Six demon.
It is also the first time that he is not fighting just to secure victory, but rather, he is also fighting for the honor of his teacher. This fight was when he was able to redeem himself and become a character who was not held back due to his fears and insecurities. He managed to not only fight for his teacher’s honor but also invent a new breathing technique to defeat his opponent.
In conclusion, Zenitsu managed to become what he always believed he could be: a protector, a swordsman, and a hero. His character arc comes to a conclusion, and his journey has a satisfying ending. The Demon Slayer series may not have introduced him to be one of the strongest, but by the end of the series he earns that title fair and square. Especially among the younger generation of demon hunters.