Who Is the Mysterious Demon Challenging Zenitsu in the Infinity Castle Movie Trailer?

Demon Slayer: Kimetsu no Yaiba is arguably the most popular dark fantasy anime of the last decade. With its compelling storytelling, well-developed characters, and brilliant world-building, the series has captivated fans all over the world. Now, after delivering season after season with better-animated fight scenes and emotionally charged moments, the anime is gearing up to take things to a whole new level in the Infinity Castle arc, which is set to be adapted into a trilogy.

As fans await the release of the highly-anticipated first film later this year, they got the glimpse of what’s to come through the official trailer that revealed several interesting moments. Among them, one stood out as it probably left fans with a lot of questions. Let’s decipher the mystery behind it to understand its significance to the overall story.

The following contains spoilers from Demon Slayer: Kimetsu no Yaiba manga and anime.

A Familiar Foe Awaits Zenitsu in the Infinity Castle

Agatsuma Will Face a Familiar Demon in the Trilogy

The Infinity Castle trailer gave glimpses of several battles that are about to take place in the upcoming film. Shinobu, who seemed more ready than ever before, could be seen fighting Doma. Meanwhile, Tanjiro confronted Akaza, understandably enraged because of what he had done to his friend Kyojuro Rengoku. Mitsuri, Obanai, Gyomei, Sanemi, and Muichiro also appeared prepared for a long battle, knowing that they might just have the chance to end Muzan’s rule of terror once and for all.

The stunning visuals beautifully captured the intense emotions that these swordsmen were probably feeling at the moment. But one specific scene probably left a lot of fans scratching their heads. Zenitsu ran into a mysterious demon who looked like a swordsman since he unsheathed a sword and welcomed him by saying:

It’s evident from Zenitsu’s expression that he can’t wait to fight the demon, whose first words clearly imply that the two know each other. Interestingly, the face of the demon is not shown in the trailer but it’s evident from his hair that he is definitely not Kokushibo, the only known demon who uses a sword. So, who is this mysterious demon and why is Agatsuma so motivated to fight him?

The Chilling Truth About Zenitsu’s Rival in the Infinity Castle

Agatsuma is All Set to Fight His Old Bully

As fans probably remember, Zenitsu had received a mysterious letter during the Hashira training following which he became detached and serious. He isolated himself and started training harder than he had ever done in the past. It turns out that the letter he had received revealed that his mentor, whom Zenitsu fondly called Gramps, had committed seppuku.

Many years ago, when Agatsuma was training under Jigoro Kuwajima, there was one bully named Kaigaku who used to mock him all the time. Because of his low self-esteem, Zenitsu never stood up for himself. Once he became a demon slayer, he forgot about his old bully, not realizing that his past would come back to haunt him all over again.

It turns out that Kaigaku had also cleared the Final Selection and joined the Demon Slayer Corps, at some point in the past. During one mission, he accidentally ran into Upper-Rank One, Kokushibo. Prioritizing his survival, Kaigaku surrendered and became a demon. When Jigoro learned the harsh truth, he decided to take his own life, out of shame.

It appears that Kaigaku was later chosen by Muzan to replace Gyutaro and Daki as the new Upper-Rank Six. When Zenitsu learned about everything, his old fear of death was gone immediately and he transformed into a fearless warrior who had just one goal, to kill Kaigaku and avenge his Gramps.

Zenitsu and Kaigaku’s complicated past creates the perfect emotional backdrop for what could be one of the most intense battles in the series so far. Irrespective of who wins, Zenitsu’s full potential will finally be revealed.