Demon Slayer: Infinity Castle’s Best Fight Is More Heartbreaking Than You Realize

Demon Slayer: Infinity Castle film hit the Japanese theaters on July 18th, 2025, while global fans will have to wait a few more weeks. The film will be released in the U.S. on September 12th, 2025, featuring the final and best arc of the series. The final arc will be released in a trilogy, with the first part having a runtime of two hours and 35 minutes. The film will pick up the story from where it left off in the Hashira Training Arc’s finale, as the Demon Slayers barely get to corner Muzan Kibutsuji before the gates to the Infinity Castle open. They are all sucked inside Muzan’s secret hideout, where they must deal with the Upper Moons before fighting the demon progenitor again.

The trailer teases the highly anticipated showdown between Akaza and Tanjiro Kamado, which could be considered the best fight in the entire trilogy. Akaza already became a fan-favorite villain in the Infinity Train film, even though he is responsible for the death of a beloved character, Kyojuro Rengoku. While the Infinity Train Arc merely served as his introduction, the final arc reveals everything we need to know about him, and it’s easily the most heartwrenching part of the story.

Warning: This article contains spoilers from the Demon Slayer manga!

Akaza Has the Saddest Backstory in Demon Slayer

Demon Slayer comes with its fair share of tear-jerking moments, especially in the form of backstories that highlight how broken the world is. Whether it’s the Demon Slayers or the demons, so many of them have struggled and suffered because of the cruel world they lived in. Even so, it could be argued that Akaza’s backstory is by far the most tragic one in the series because of the way he constantly suffered for a majority of his life.

Akaza, known as Hakuji when he was a human, used to commit theft in order to get enough money for his father’s medications. He got branded as a thief, and his father couldn’t bear the thought of being a burden on his son, so he took his own life. Akaza fell into further despair and fought endlessly with people who crossed his path. Just when he had nowhere to go, Akaza was taken in by a dojo master, Keizo, and fell in love with his daughter, Koyuki. Despite his shady past, he was warmly welcomed by the family of two and finally found a home.

However, a rival dojo poisoned the well, which killed the dojo master and his fiancée. He killed everyone responsible for that, and Muzan learned about him. With nothing else to lose and no will to continue living on, he became a demon. After transitioning into a demon, he should’ve lost his memories, but a small part of him remained human. The tattoos on his body are a reminder of who he was before meeting his fiancée, since they are similar to the ones he got as punishment for being a thief.

The pattern that appears when he activates his Blood Demon Art is exactly the same as the hair clips his fiancée used to wear. Even the fact that his blood boils at the mere mention of killing and eating women is because a small part of his human self is alive, which loved and cared deeply for Koyuki.

Akaza’s Tear-Jerking Farewell Concludes the Series’ Best Fight

Tanjiro was already motivated enough to kill Akaza after what happened with Rengoku. Giyu Tomioka also joined the fight and lent him the support he needed. Both fought the demon as equals and grew significantly stronger during the battle. Giyu was able to pass through his psychological barrier and awakened his Demon Slayer Mark while Tanjiro explored the unique powers granted by the Sun Breathing Technique. The fight is incredibly intense, with some of the most thrilling scenes in the story.

Blending Akaza’s backstory made it all the more tragic. In the end, Giyu and Tanjiro were on their last legs, but Akaza had one more trick up his sleeve. Just as he was about to launch another devastating attack, his memories as a human return, and he sees Koyuki begging him to stop. Akaza self-destructs and thanks Tanjiro before turning into dust. The fight concludes as we see a tear-jerking reunion between him and Koyuki in the afterlife.